I'm not sure how many assumptions that are present in the minds of strangers......but it is a fairly well known fact through many tests that (good) glue joins are way stronger than the original wood grain. Its fair to say any repairer would know it, and typically this sort of info is almost universally relayed onto clients who would naturally worry about whether any repair would hold. So to assume people are thinking that the tone shift is merely a perceptive compensation is more likely false than valid.
The issue many thinking people would have with the 'better tone after a break' theory, is that it typically is weeks to months between break and returned repair.....especially if nitro touchup is needed. As many people seem to find tonal variance between a rig from one day to another (not only ears and perception, but environmental conditions are guaranteed variables), trying to remember a guitar from so long ago and compare it to now, where it has most likely needed/had a full setup and fretdress plus fresh strings is a long bow to draw.