However, meal-offerings – which were also unleavened bread – were made specifically with lukewarm water. If it is good enough for the sacrifices, why not for regular matzah? The Mishnah related to this meal offering is:
ALL MEAL-OFFERINGS MUST BE KNEADED WITH LUKEWARM WATER AND MUST BE WATCHED LEST THEY BECOME LEAVENED. (Menachot 55a)
The “watcher” is an official, a priest, who insure that the dough does not rise.
If this was said of [very] careful men [priests], shall it [also] be said of those who are not careful?
In other words, the priest could be trusted to insure that the process is followed correctly, but the ordinary Israelite, baking matzah in his or her own home, could not.
Very interesting to see this kind of professionalization. This would be expected surrounding the sacrifices, which could only be done by a priest. But extending it to restrictions of Passover baking is unusual!