No one is saying it has locked in already. They're saying we're on course to achieve lock in next period.
And technically even after it has locked in we have to wait till November before the 1st tx's and so the 1st Blocks with it in.
Up to that point if a majority of the miners downgraded it would not manage to actually maintain the longest chain so if someone published a currently valid tx that was invalid under taproot we would have a chain split... (I think I am right on this?)
So if you enjoy a good conspiracy theory can run with that scenario... which really would be chaos... BitcoinCash/SV all over again but with Core having the lower hash rate!