Read a piece last week that solidified my thinking on this one -

Agree or disagree (disagree, btw) in beliefs held by Christian Scientists, at least their refusals to be vaccinated are consistent. Everyone else is trying to use "religious exemption" as a blanket "get out of jail free" card to excuse any random idea that pops into their empty heads.

To your point though - masks have not a damn thing to do with this - pretty much the same as washing your hands and maintaining social distancing - all perfectly acceptable according to CS principles.