No that's incorrect. Use his/he or her/she if the coat appears to be one that would be worn by a male or female. If uncertain, use male pronouns, which are gender neutral in that scenario.
Incorrect according to who? You? Your Sainted Mother? Sounds innovative to me, and hardly traditional. Saying male is somehow gender neutral sounds even more bizarre.
No, usage makes correctness in language, not people trying to invent some weird conlang they wrongly insist is correct English.
I must have missed the brief somewhere, but there was/is a very clear trend to replace the default male pronoun for gender neutrality with the female pronoun she. Just recently I noticed this in Judea Pearl’s Book of Why. When and why did this start happening? It feels so forced and unnatural. You can sense he’s trying to kiss someone’s ass or appease an authority. At least mix it up a bit at best if you truly give a crap.
No, usage makes correctness in language, not people trying to invent some weird conlang they wrongly insist is correct English.