Absolutely, it's a silly argument. I knew plenty of people who slaked off in-person, most managers aren't literally standing behind you watching your screen. It's IMO a bad metric anyway, I'll read Reddit, HN, watch Youtube, etc. when I'm "supposed" to be working because I need to take a break, and I get more than enough done and work enough hours that it doesn't impact my work.

The things you can't hide are having no meaningful update for stand-up every day, not completing any cards, not participate in conversations/planning, etc. If's that not catching up to them then that's on management for not paying attention.