This is an exposed deck pier we're talking about--not in a crawlspace under the home. Seems to me it's decidedly a stretch to be applying "under floor" requirements in this case.

As for termites, they would have to make it vertically whatever distance it is up to the floor joists, and then horizontally probably a minimum of 8 feet or so to get to the house itself. Across pressure treated wood. Without being seen. Doesn't seem likely to me.

Properly compacted concrete in a form should have smooth sides that are not likely to absorb much water, and would not be likely to suffer from freeze damage. Having soft, porous brick with raked mortar joints on a chimney is a different matter.

I'm not saying don't remove the forms. In fact, I did say they should be removed for cosmetic reasons. However, I would not make a big deal out of possible consequences if they are not removed.