Yes, you can not get into someone else's Mac. However, what if the last opened application was Terminal? I can think of several scenario where you can do "damage" without logging in—if this bug is real—depending on the last opened application.
So you're going to start typing terminal commands into peoples locked macbooks on the offchance that they've hit this bug and are running a terminal?
Its a flaw that needs to be fixed, for sure, but lets not over-exaggerate the severity as an attack surface. Its much, much more likely that it will cause accidental problems when the owner types something (like in the tweet).
> if this bug is real
Why wouldn't it be? Plenty of people here and on twitter are reporting having hit similar issues (with OS X and even linux, so it doesn't seem completely uncommon).
