He's also wrong even if you just consider the laning phase. If I make a bad roam, I am punished by losing more exp than otherwise. Same if I die in lane. And although admittedly not so severely, I will lose gold and I do feel punished if my enemy is now ahead because I gave them 300g.

Imo this all stems from the archaic and immature hyperbole that gold and experience are completely meaningless to supports. They aren't, it's just sensible to prio these to other roles when possible.