In a typical situation (ie: where you don't have oil passage/pick up blockage due to bits and pieces of old silicone) sure, I could see where "most of the wear" on the bearing could come from cold starts. Bearings wear out, thats not unheard of. However, this regular wear isn't going to spin a bearing 5k miles down the road. I daily drive a 213,xxx mile lexus gs400, im sure those bearings are worn compared to new, but hey, they haven't spun
Also, keep in mind the pretty high compression on the FA20. 12.5:1 is a pretty tight squeeze.
With all that said, in all of these cases it isn't the cold start thats killing these motors. Its a shear lack of oil. Thats just a dealers way of trying to talk their way out of covering a shortblock replacement.
Going through doing this recall myself in my garage right now, (if you haven't seen my other thread) I can certainly understand how easy it is to get bits and pieces of this silicone stuck in places they shouldn't be. I am pretty confident that most of the failures are a result of the old silicone bits being left where they shouldnt be vs using too much FIPG when reassembling. I am on my 3rd round of blocking out all the passages after doing a very thorough clean up and am still finding small bits here and there, and with only what? 13-15 hours of labor covered for the ENTIRE recall procedure I can certainly see this step not happening as thorough as it needs with the dealer.