There was no fake slide by Allen, but there is a point, the defender is often in a lose-lose situation when attempting to takle a QB.
When Josh slowed, for sure the defenders processed "ok, he MAY slide", in that case, I could not takle him.
This decision could lead to a split-second indecision and Josh is gone.
I would call a late-hit on the QB only if it is blatant.
In my opinion the one called on Prescott on 3&2 must be a no-call, the one on Josh is borderline.