My issue with Kohler is parts availability...and, while some people never have problems with their toilets, if you simply look at the trapway design, you'll see that on many of them, the outlet makes a sharp 90-degree turn at the flange and the Toto designs make a much more gradual turning there. Depending on the size, shape, and hardness of the waste, things just go down the Toto toilet's trapway faster and with fewer problems. Some never have a problem, others have problems on a regular basis with the Kohler design. Things do not make 90-degree turns and maintain decent velocity unless done properly.
I do not ever remember Terry saying Kohler had anywhere near that level of defects. I do remember him saying that Toto has the lowest of the MANY brands he sells. The 20% figure I remember was about his breakage factor and the reason why he no longer ships toilets, and limits his delivery area.
My last experience with Kohler was on a special order. Each time the supplier called Kohler, they said it would be shipped tomorrow. This went on for MONTHS. IN a week or so when it didn't show up, they called again, and got the same story...it will be shipped tomorrow. Then, they sent the wrong thing. THen, once I got it, I was not particularly impressed...parts fit, paint, fit and finish. At that point, I didn't want to send it back and suffer the same, horrible customer service I got again. Since then (this is a shower door), the paint chips, the bearings are crappy and make noises, and even with the several holes, the system did not have a proper position to adjust the height in the track well. The holes in the glass were all rough. If you know anything about glass, you want a nice clean hole. It hasn't spontaneously shattered, but it should never have made it out of the factory, in my view. So much for quality control.
I do like some of the designs, but from an installer's viewpoint, some of their stuff is HORRIBLE, and almost unreasonable. For example, they have some shower body sprays whose rough-in must be less than 1/16" accuracy to fit properly in the tile. Do you know how hard that is to do when trying to get multiple trades to communicate? This is the only company I know of that deems it reasonable to set such strict requirements. They design in a vacuum, and not for practical use. Then, if you search this forum, you'll find stories of Kohler bending over backward to help people, then you'll find others where they say, sorry, you'll just have to replace the thing...we won't help you. So much for a decent, stable design and continued availability of replacement parts. Few places carry Kohler replacement parts since their design changes so often, the inventory would be HUGE, with no expectation of ever recovering the investment. So, do you want to wait a week or more when you need a part? If you do, buy Kohler. My personal opinion and experience.