If drywall mud getting wetted by a laytex paint/primer/thinset/whatever really caused a bond-breaker, the paint on millions of rooms would be falling off when someone rubbed against it or bumped it. Trying to minimize the possibility is a best practice issue, how important in the real world, not sure, but I'm sure the legal gurus want it. Except when you're actually trying to remove drywall mud, how often have you had it fail when paintin, or adding thinset to it? It takes a lot of water and a lot of rubbing to get it fluid enough to do anything. Thinset has little 'excess' water in it...the water that is there is chemically incorporated into the cement as it cures. If you were using a medium bed mortar you might have an issue, but it still probably wouldn't. To preclude the small possibility, a prudent practice is to mitigate problems, and Schluter recommends a primer to seal away the moisture. Best practice is to not put it there in the first place. With the cost of labor to scrub the stuff off, it might be just as cheap to just replace the stuff with virgin drywall, then you've not got the problem at all. Tear it off, screw some new stuff up, and go for it.
Nobody should be trying to do anything to dusty drywall, neither paint, nor wallpaper, nor thinset. So, trying that is just an indication of poor practices, and anything you try is open to subjective results.
If you want to determine 'ultimate' stength, then wait the industry standard for cement products - 28-days. ALL products are spec'ed at 'full' strength after curing for that timeframe. You get a fair portion after 24-hours, and more at 7-days, but full strength is 28-days. In fact, cement products continue to get stronger the longer they cure. And, the bond between a waterproof membrane and a nearly impervious tile will achieve the full-rated strength more often with a dryset than with a modified that has trouble drying. Given enough time without stress loads, it might reach full strength. If you're talking about bond breakers, a modified over a waterproof membrane and a good porcelain large format tile, now you've got one if it is distrubed, as it needs to dry, and that can literally take more than the spec'ed 28-days.