That report was read years ago, but the details stuck with me. Not worth trying to find. Can you find that old magazine or article you read 5-10 years ago?
A couple of personal examples of stressing the system:
1. For the first 8-years or so I had a waterbed in my bedroom. I ran the numbers, and the bed was about 30#/sqft. Then add in the frame, the carpet, the subflooring, and it was close to the 40# dead load. Not all that much in the rest of the room, but it was not empty. It so happens that each wall is load bearing around the perimeter of the room. There's a non-load-bearing partition wall slightly to the side of where the bed was placed under this room. The wall ran parallel with the joists, and was not on one. I noticed a crack in the opening between rooms down below in the drywall, and when I did some remodeling of the rooms below found that that non-load-bearing wall had been pressed about 3/4" down...it had literally bent the subflooring into a z-shape, since it was fairly close to a joist. This from a design/build to the specs of 40/10 with a load less than the design. It took a bunch of years to occur. The wood has some elasticity and plasticity to it, but apply a load at or near its design limits, and when it bends, it does not bend back. The plasticity of it allowed it to bend rather than break because the load was applied continually over a long time. The crack didn't close up when I replaced the mattress with a conventional one, either...the stuff had taken a set.
2. Have a small deck off the dining room that had cantilevered joists - about 3/4'rs under the interior, and 1/4 outside (sitting over the outside wall). Edges supported with diagonals to the walls. Over about 15-years, probably from a snow load that was intermittent, the dining room crowned about 3"! Call it an inverse load, if you will. The deck was redesigned by an engineer, and replaced. The load path strengthened and hung from the rim joist with steel shell for support. No further problems.
Both of these are to illustrate that it can take some time to make any observation of overloading a structure. You hear of reports of decks falling down, partly because they tend to have an accumulation of people partying, but overloaded is still overloaded, and things can only bend so far. My personal examples don't show catastrophic failures, but that things do bend, and eventually if the load is applied continuously and over the design strength, it won't spring back.
Let's take a shower, from FL's state design guidelines (the first ones I found on a quick search), 1" mudbed is about 12#/sqft. In a shower of any size, using a conventional clamping drain, it probably averages 3", so you have 36#/sqft. Now, throw on some tile, averaging say 4#/sqft, you're at the max design dead load of any room without the subflooring (or extra blocking you want). THen, add in that extra layer of plywood, the room, already overweight, now is even more overloaded. We haven't added in the partition walls for the side of the shower....let's say it's 4x8 and you've tiled to the ceiling...that's about 320# if you're using say granite or marble on only a few square feet and we haven't included the cbu, studs, waterproofing, etc., you need to actually build a shower wall. In your high-end house, let's say you have CI drain lines...throw in another few hundred pounds for the bathroom and that big, two sink vanity with 3cm granite counter, maybe another thousand pounds by the time the silly thing is loaded up and you count the two sinks, faucets, tiled or stone backsplash, etc. Add in the water closet (toilet), with the tank full, probably close to 100#. Maybe add a bidet. THen, cause it's an upscale house, you have a nice big CI whirlpool (no cheesy plastic tubs here!) at 400# or more then add a mortar bed, and a tiled raised platform. It all adds up. Average this out over the room, and you can easily exceed the 40+10, and you haven't filled the tub or put anyone into it.
So, as I said, there's a cost/benefit/risk to any build. Adding in more when you don't need it is not good design, it's dangerous with short sight. These things do not happen overnight...they take time, like that barn in the country with the wavy ridge line. They happen way past the typical 1-year warranty of most installs, and may take decades. Far enough into the future, where it gets shrugged off, or they've decided to remodel anyway...but, they are real.
Wood in Europe is usually reserved for decorative surfaces, and is not used as structural very often today. They don't have the luxury of large forests they're willing to cut down anywhere near the scale that is typical in the NA continent. They tend to have lots more brick and concrete structures. This tends to have MUCH higher design load capability than the typical stick built house in North America. It doesn't seem strange to me that they may have adopted different methods to do things...weight doesn't factor into things anywhere near as much. Trying to emulate their methods when the infrastructure is different can be problematic. In my view, anyway, that's one good reason why some of the installation instructions differ in region to region. That does NOT mean one is better than the other. You have to know when enough is enough and adapt to the situation. Telling the world your way is the only way and any other is junk is pretty narrow minded. Your knocking the manufacturer's instructions as unreliable and incorrect when testing has proven over and over again that it works is pretty pompous. Advocating belt and suspenders, when it adds cost, time, materials, weight just doesn't add up except in your mind.
Enough for now...this is really getting old. In my view, needed, though, as counter-point. Just read the manufacturer's instructions, follow them. If you don't understand, seek guidance. It works as designed.