One of the WDW mods reported that gaiters have been seen on guests in Disney Springs since it reopened. No one has stopped those guests and no one has reported any issues so far. It appears that Disney's specifications on masks/face coverings is to prevent guests from showing up in face shields only or other types of homemade type coverings that leave gaps on the sides of the face and below the chin.
Personally, I would bring a variety of masks and gaiters for a WDW trip, just so I could keep changing them out according to weather conditions and comfort/discomfort level. So far, even in a/c, I haven't yet found one type of mask that is comfortable every time.