It takes a simple lithmus test to see why something might be sexist, simply apply it to other groups and see if the racism shows...
Would telling a woman every time she gets condescending that she is "womansplaning" be sexist?
If everytime a black person got uppity at you and tried to explain something and you called it "blacksplaining" would this be racist?
To me anytime I use the pattern above on virtually any race, sex, orientation, anything, it comes across as rude, childish, and prejudice.