Interesting.... and there is that 70 AD... they say CE dates.... hmmmmmm After the temple destruction time period? Why?
The problem with identifying such pools as ritual baths is that the earliest literary evidence for mikva’ot comes from rabbinic legal writings, which do not date before 70 C.E., while the pools of the type described above emerge around 100 B.C.E. and then proliferate from the beginning of the Roman period, only to disappear shortly after the Bar Kokhba Revolt (132–135 C.E.).
To understand that you have to understand the reason that the Mishnah and Talmuds were written in the first place.
After Bar Kochba, most Jews were forcibly moved out of the province of Judea. So much (including the teachings of the Rabbinic sages) from the entire 2nd Temple period, was transmitted orally. The Jews got scattered thru out the Empire and in order to keep an understanding of life before the destruction of the temple, they started compiling the Mishnah. IT was published circa 200 CE.
Since the Temple Mikvaot were additions to the 2nd Temple grounds, their use was a matter of oral tradition also.