A couple of years back I looked into the depth of penetration of epoxy. My findings mirrored some others with a LOT more credentials than me( which are almost ZIP). Epoxy penetrates, thinned or not, about .003 to .004 inch. I just checked a test piece of pine plywood that had 1 coat of Rustoleum oil based paint. Penetration was about .004 to .006 inch. The other end of the same test piece was flooded with Danish oil and allowed to dry. The nearest I can tell, it penetrated approx. .070 inch...........basically right down to the first glue layer. Now, if this finish penetrated into all the empty spaces in the first ply, (spaces that could hold water) , then there would be no place for the water to "go". Just a little something to contemplate.