That’s an interesting take for sure, and I think I read about this caveat elsewhere. Let me just add that Paul Gilbert has a very broad musical range - there surely is a lot of high gain shredding (at least in earlier days), but he‘s also doing amazing work with clean settings and acoustic guitars. His hearing is not the best though, so maybe subtle differences in dynamics escape him :)
Personally I think that most problems people report about Kemper‘s sound stem from their speaker setup. If you use it for audio recordings or for loud stage setups, you most likely won’t be able to tell any difference. There are lots of blind tests out there and people often think that the Kemper is the real amp.