The whole conversation from the vegan side has been that those proteins and other substances essential to cats are already commonly synthesized for things like animal feed or even human energy drinks. Your own source says it’s impossible without synthetic supplementation, but the deleted comments from that dumpster fire were specifically about synthetic supplementation.

I’m not an expert in this stuff but I can see when comments aren’t actually engaging with arguments from the other side, which is why I think that the vegans have the better argument in this whole saga.