Yeah, it’s when the population gets high that they start trying to chew the foam. I’ve got some pure foam boxes where they chewed out half a wall of the foam and built comb right on the foam! I use plastic sheets (painters drop cloth stuff) for my inner covers and I didn’t think they could chew through that, but low and behold, they have chewed through the 3.5mil thick stuff in spots. I have moved to 6mils now and haven’t had that problem again. My guess is the clear tape, or contact paper, has a good chance of preventing the chewing if you can keep it from falling off the foam. The first areas they’ll chew are around the entrance. As the population gets bigger, evidently they would like a bigger entrance and they’ll chew to make it bigger. They also like to chew the top covers which is why I went to a plastic sheet for an inner cover. Works well because you can peak in on the bees and it prevents them from gluing the foam top down.
Actually a much bigger problem with unfaced foam is the wax moths. If/when they take over a box, they'll completely destroy the foam because they can burrow through just about anything. Foam to them is like a hot knife to butter. :( They'll burrow and tunnel all through the box if it isn't cladded with something tough on the interior side. I've gone with 1/8" hardboard cladding to stop the moths and chewing. It's cheap, dependable, glues easily to foam, sticks reliably, not a thermal bridge, and holds up to the moisture fine. I've even tried the hardboard for exterior cladding, but the boxes tend to get a little bulky and way more time consuming to build.