Editing Mesechtas Terumot (section)

==== Jerusalem Talmud's Opinion ====
In the Jerusalem Talmud, there is a dispute regarding Rabbi Yehoshua's opinion about whether one type of produce can nullify another when it is known which one fell (whether Torah or white fig), or whether when it is known which one fell, even Rabbi Yehoshua holds that they do not nullify each other. According to this interpretation, the dispute between Rabbi Yehoshua and Rabbi Akiva is that Rabbi Yehoshua believes that since one forgot, it's as if it was unknown at the time it fell, while Rabbi Akiva holds that since one knew at the time it fell, they do not nullify each other, even though one later forgot. The Rambam, who ruled according to Rabbi Akiva, also ruled in accordance with the Jerusalem Talmud, that if one knew what had fallen after it fell and then forgot, all are considered mixed with terumah and do not nullify each other.

According to this, Rabbi Akiva's reasoning is seemingly difficult to understand: why when one knew and forgot are all considered mixed with terumah and do not nullify each other, since now they are all in the category of doubtful prohibition? And one cannot say that since the fifty were already mixed with terumah (when one knew), they cannot be nullified afterwards when one forgot - because it is explicitly stated in the Mishnah: "If one se'ah of terumah fell into less than one hundred (se'ah) and afterwards non-sacred produce fell there, if one did so unintentionally, it is permitted." This means that even though initially there were not one hundred to nullify and they became mixed with terumah, when more fell there unintentionally afterwards, they combine to nullify. So why don't we say here too that when one forgot, they are all in the category of doubtful prohibition and combine to nullify each other?