The strongest terms? Does he think it is as bad as evolution (which he knocks down in the first Maamar)? He says it is foolish and comes from outside. That’s not Mamesh the strongest terms. Besides, as I mentioned other times and hinted to above, he might have held of it as a Sod, like the Ramban, and it is not a regurgitating conscious entity, which is what he was addressing.
By the way, in retrospect, many Maamarei Chazal are only understood with Gilgul, when they say this one is that one. This is where Mekubalim and rationalists meet.