To me it is not a skill. It is just an unpleasant thing to do that I will do if I have to.
I agree that opening eyes is perhaps not a _skill_ in the same category as a regulator recovery or fin pivot. However, some people do find the burning sensation of salt water in the eyes after they replace the mask and only managed to partially clear the mask by the first attempt to be an additional trigger to panic. The burning sensation in the eyes together with the water that seems to want to go up their nose when they've just completed a mask remove and replace (stressful for some students) that still needs to be refined a bit does sometimes add another factor into the mix to consider. Granted that this still falls into the mask remove and replace skill to be mastered (whatever that means), but a mask remove and replace with eyes closed is not always the same thing as a mask remove and replace with eyes open in salt water IMHO. It takes getting used to and practice for some people to suppress the urge to panic and deal with the situation all the way through to the end in a relaxed manner. In that sense I do somewhat consider it an augmented take on the regular mask remove and replace _skill_that is IMHO well worth helping students to get used to in addition to their regular mask clear and remove skill. Of course I would not refuse to certify them if they couldn't do it, I would just try to help them get it right for their own sake. It is the same reasoning behind why my wife had to perform her mask remove and replace at 100ft with her instructor for her CMAS 2 star skill demonstrations; an added task load or a change in the variables makes preforming the skill more difficult to do and doing it despite the added stress load does arguably confirm "mastery" of the skill to some extent (although in her case this was a required part to be certified)