I've never used that but I'm assuming that they are concerned that a wet paint layer applied to that stuff after it is fully dry may rewet it enough to cause it to debond  , before you want it to .

It's an acrylic resin similar to what is used on decals   -- when it gets wet it absorbs water and expands the resin and breaks its adhesion .

You should be fine as long as you use thin coats atop it .