In this case, Mark tried to give them the benefit of the doubt, explaining that even if the circuit is a reference design, spending time to match components might make it better than it would be otherwise. It wasn't a bashing, but seemed like a repair video in good faith.
Reading the website of the guy who sells the amps, it's clear he has some ego issues:
https://www.audiodesign.co.uk/index.html
I'm guessing he expected to see Mark fail to repair it, and instead talk about how amazing and advanced his product is.