There are two factors in putting poly over epoxy, mechanical and chemical bond. First, there is no chemical bonding between the two (not like a poly lam and poly HC). If you get a good enough surface prep for a mechanical bond, it’ll work and my experience is no higher than 80 grit. Poly hot coating over an epoxy lam without sanding I’ve not done and it seems rather risky on a wood board.
The primary reason for using epoxy on wood is that it is a better bond than poly. Poly is way too sensitive to any oils that may be in the wood. Often these oils will cook-out and cause a delam from heating during the curing reaction or sometime later. This is seen in the repair business all the time on wide stringers. Wiping the wood with acetone will remove the surface oils, but it evaporates before it can penetrate deeply enough. The idea of thinning-down poly cheater coats on wood is to get that deep penetration. Wiping with something really nasty like Xylene before an epoxy lam may give better penetration, but I think even better would be a Xylene-thinned cheater coat then sanded at 80. The slow cure of the epoxy will definitely penetrate better than a poly cheater and the exotherm will further cook out any oils. Be careful Xylene is very toxic, up there on the list with styrene.