His argument, as I understand it, is that he knew about the covalent bonds between proteins but didn't mention them because he was simplifying things for a lay audience, and that those covalent bonds don't matter because they aren't the "load bearing" elements in flesh.

There are two problems I see

1. His earlier statements suggest he actually had no knowledge of that whatsoever

2. I think his revised explanation is still wrong, because the extracellular matrix that holds cells together and connective tissue are composed largely of proteins that have these covalent crosslinks and rely on them for strength. When you tear a ligment it's not just van der waals and hydrogen bonds being broken, those alone would be far too weak.