Someone asked if the bees chewed it.

The internet answer is yes

However I have used pink foam exposed to the bees in hives for 2 years and note very little chewing.

All of my metal covered lids have 2" of pink foam, even nuc. Propolis adheres very well to it. A separator sheet of heavy plastic would prevent chewing 100%

I had a bigger issue with ants moving into the gaps. I used paint to seal the gaps, but caulking with something might work as well. Ants will move into the hive in any space the bees cant access. If you use fondant on a top board don't close the hole. If you allow the bees access the ants will not move in. I had ants rearing young on top of my fondant package!