we're probably being adviced not to use it to avoid messing up our trophies or "activations" of the games we downloaded. Offline, non-trophy, non-downloaded games work fine for me, and the PS1 version of FF6 should fall into that category.

I think it's very unlikely for this bug to brick the entire machine. The OS is in no way inoperable, but the problem with the date messes up how it handles DRM and trophies, so that the games are unable to recognize the trophy files as valid. Therefore it should be possible for sony to make a "hack" around this problem, or fix it entirely, without having to send the consoles in for servicing. If not, well, nice to have known you, Sony.