soft matzah

Question

I have become aware that there is such a thing as soft matzah. It is kind of a large pita, and is used by the Temani Community on Pesach. Can Ashkinazim use soft matzah on Pesach? There are two reasons why it would seem ok to me: 1) The Halacha and Mishna'yot seem to indicate that during the era of the Mishna, soft matzah was in fact used for the seder. 2) It takes less than 18 minutes to bake soft matzah (and pita for that matter). So if the flour and water were properly guarded to make sure that no chametz contaminated them, what would be wrong with a soft "bread" which took less than 18 minutes to bake?