UPDATE:
Actually, it is not a glitch.
When pressing the button for calling Siri, you enter fingerprint which unlocks the phone.
I didn't notice at first, but I reproduced it whitout putting my fingerprint on the button, and it asked me for a code.
So I guess it is normal and won't work if fingerprint isn't recognized.
Glass maybe tried it too without putting fingerprint or something, but he could have been more precise about it