I'm not sure that I understand what you are arguing here. Assuming there is no masking policy, the act of not wearing a mask is no longer a signal that someone is more or less cautious than someone else. This is assuming that accompanying that policy is a general public sentiment that masks are not effective.

The act of wearing a mask despite no policy would indicate greater caution, but the inverse is not obviously true.

It seems the existence of a masking policy, public knowledge about the implications of exposure, and the presumption that masks provide some mitigation are all things that are required to then make some conclusion about whether or not the unmasked person across the room is relatively un-cautious.