IMO he is wrong. X, TG and other centralized platforms require email/phone number for preventing spam accounts and recovering your password. And these recovery mechanisms get hacked. Nostr doesn't have those. You will lose your key, if your phone is stolen. Period. It's solely up to you to backup it.

my question as well and I think only time will tell. I think it's a solid point to make, but there's no way of knowing the truth unless/until an alternative better option comes along