There is no excuse for the behaviour of the Emergency Calls button. None. How anyone can defend it is beyond me.
'112' is the international GSM standard emergency number... if you dial this number from any GSM phone, it will route you to the appropriate emergency number in the country that you're in (eg. 911 in the US, 000 in Australia - etc.)
Apple merely need to program in the allowable combinations - just like every other phone manufacturer on the planet - 112, 911, 000 - etc.
Allowing any call to be made from a "locked" phone is preposterous and, if designed that way (which it appears to be), needs to be changed. Whether classed as a bug or a "feature" - it needs to be changed.
And for those that say lock the SIM... how does one do that, and still receive calls? Locking the SIM means that the GSM part of the phone is inoperative (other than for emergency calls).
Oh, and good luck trying to get the $5+ dollars per minute calls to premium numbers credited back to your account by your service provider that the thief is likely to call.