The only problem with seating foam is that it is Open cell foam. If you oil your rifles before putting them in the cabinet, which you should always do, the structure of the cells can and do absorb the oil off the blacking. This can and occasionally does leave imprints/marks on the action where the oil has been drawn into the foam. The other reason for not using foam is humidity or moisture getting into the foam and the possibility of rust forming over time.
Been there! Had that unfortunate T shirt.

Mark.