I find your take on this very strange. Given that, again,
Coinbase themselves called this "a flaw in Coinbase’s SMS Account Recovery process", it would be bizarre that this was just "standard" run-of-the-mill SIM-swapping, because of course SIM-swapping is always an inherent danger with SMS 2 factor.
Coinbase is very clear in the breach notification that attackers had already acquired users' (a) emails, (b) passwords, and importantly (c) already have access to the users' primary email accounts. At that point, the only thing left preventing account takeover would be the 2FA challenge, and since Coinbase said there was "a flaw in Coinbase’s SMS Account Recovery process" I find it a bizarre conclusion to think that flaw was just a standard SIM-swap.
Edit: Actually, pretty positive it was not just a standard SIM-swap given that, if it were, Coinbase would not have specifically called out "a flaw in Coinbase’s SMS Account Recovery process". If it were just normal SIM-swapping bad guys would have just used that to defeat 2FA during the login process - there would have been no need for them to mess with the account recovery process. That's actually not that uncommon a bug, where 2FA works great to protect login, but there is an oversight that makes it not required during the account recovery process (by definition you're letting people into an account during the recovery process even if they're missing one of their authentication methods) that makes the whole 2FA moot.
