Justin, This is just a guess, but maybe they are S. tuckermannii. It would help to have closer views of the stalks.
Yes, it is supposed to be corticolous, but many species of corticolous lichens will occasionally transgress to rock.
Of course a good test for this would be to do DNA sequencing. The existing taxonomy is based on very few sequenced specimens, so it is quite possible that the situation is more complex than we realize.