think the logic is that trans femme people are more likely than most to need to shave all of those areas. Traditionally cis men having arm and leg hair is acceptable while most shave at least some part of their beard, and many cis women do not need to shave their face but are expected to have smooth arms and legs. Trans men, if on T, I presume would be in the same category as cis men as T will encourage that hair growth.