Once, there was some weird glitch with my iCloud account, and my Mac was locked without any reason.
The PIN code consists just of 4 numbers (10000 values total), so I solved this problem with stupid Bruteforce method.
Spent several hours on that, because every 5 tries, you need to reboot your Mac to reset the "waiting" counter,
and reboot takes almost 1 minute. Was not bored at all: there was a PC near me and I used it for Internet browsing.
But, after this situation, I am really worried about this feature: since the real thief could do the same thing as me
and unlock the Mac in less than one day, then this feature does not bring any security at all! 😡
Should be more numbers, or letters as well - otherwise, it just too easy!