I think that all of these scientific facts are probably true.
But it is also probably true that the homebrewer should not reuse yeast to the extent that it is done in a laboratory setting or brewery setting.
A brewery is presumably closer to a laboratory setting when it comes to the care and use of yeast strains. Even if harvesting is done by a novice in the brewery, it's still done using properly sanitized equipment and the cells are then kept in an otherwise sterile, low-stress environment. Not to mention that the ridiculously higher number of yeast cells affords the brewery some leeway compared with the homebrewer. In a brewery, the high yeast population would presumably overwhelm the same small contamination that would noticeably affect the population in the homebrew setting.
In the homebrew setting, people forget to sanitize something or leave something open on the counter and their yeast strain is contaminated in one generation irrespective of the mutation rate.
Don't get me wrong, I love the science of brewing. But I think to apply basic laboratory science to the homebrew setting is a bit of a stretch. Granted, if you use techniques akin to a laboratory - or even those skin to a brewery, you will probably have fewer issues reusing yeasts over many more generations than is typically recommended.