just my hapence: If you look a little later on, he brings a letter quoted from Mahara”m Alashkar that the Rambam wrote to one of his talmidim and than says he has that ksav yad.
????”? ????? ?”? ???? ??? ???????? ???????? ?????? ??? ???? ?????? ????? ??? ???? ????? ??? ?????? ??? ???? ?????? ????? ???? ??????? ????? ??????? ?????? ?????? ?????? ?????? ?????? ???? ????? ?????? ???? ???? ?? ?? ????? ?? ????? ??? ????? ??? ?????? ???’ ????…???, ??”? ????? ???? ?? ??? ???? ???? ????? ?? ?? ???? ??????? ????? ??? ??? ?????? ??? ????? ??? ?????? ?? ????? ?? ?? ???? ???? ?????? ?????? ????? ?????? ????? ????? ????
The truth is, you’re right, I don’t think there is anything empirical, because this could have been a conspiracy stretching back a thousand years. When I approached my Rosh Kollel with this shtickel I asked him if it negates all the Rambam we have today and he told me that it means that there are to valid opposing shitos of the Rambam. He called it a machlokes between the Rambam and the Rambam. So in that case I would say that maybe all the nosei keilim were not making a mistake, they were only asking according to that shittah of the Rambam because it is also Torah. The fact that no one mentions could mean that the Rambam was at the end of his life (as he says) and didn’t have the capability to make this new shittah known throughout the world. So instead he wrote a letter or two that never became widely known.
Sam2: I check Reb Berel Wein and it looks like it wasn’t him, but I’m almost 100% sure I heard it somewhere from someone. Maybe it was Rabbi Tatz. I’ll try to find it.