What the hell!!
Any player who pushes ALL of his/her remaining chips forward, so as to be considered a "bet", is making a physical statement of "all-in". Does it make any difference whether the amount of the chips are less than, equal to or more than the amount the player is facing, I think not? If the player doesn't know the proper procedure to vocalize his/her action, since it is obviously unclear, then that player needs to learn a lesson.
IMHO, there are already too damn many rules just for particular situations that arise rather infrequently.
I feel sorry for players who have to learn lessons the hard way, but if we have to promulgate a rule for every possible situation, pretty soon the rule book will be totally unworkable, if it isn't already.
Chet