Maimonides' method of counting the Nida

It is known that the Rambam's method is that the woman begins to see the first blood, from that time the cycle of the seventh and eleventh and eleventh begins without any interruption or change throughout her life. And here I saw Rabbi David bar Chaim who wrote here that the entire world from then until now has been mistaken about the Rambam's intention and is based on a printing error, according to the revised version in the Rambam that he cites there. And I looked there and did not see any significant change in his Rambam.
What is the Rabbi's opinion on this matter? And Tashochah to him.