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No, it wouldn't be fine to say that, nor to make that assumption based on a photo. This is why the Report of the PCC Ad Hoc Task Group on Gender in Name Authority Records explicitly says : "Do not assume gender identity based on pictures or names."
Ted's questions ("Would I say he has short hair and a moustache? If he doesn’t have a moustache, is the short hair not enough?") point to why it is highly problematic to assume someone's gender based on your perception of their physical appearance. (One can have both a mustache and short hair and be a woman, or nonbinary.) I realize that making this assumption seems like common sense to you, but such an understanding of/approach to gender is simply no longer considered valid or acceptable, but actively harmful to people whose gender might not be "obvious."
If you're not convinced, in addition to reading the Report of the PCC Ad Hoc Task Group on Gender in Name Authority Records, please also check out the following:
Amber Billey, Emily Drabinksi, and K. R. Roberto. "What's Gender Got to Do With It? A Critique of RDA Rule 9.7." Cataloging & Classification Quarterly 52, no. 4 (2014): 412-421.
Kelly J. Thompson. "More Than a Name: A Content Analysis of Name Authority Records for Authors Who Self-Identify as Trans." Library Resources & Technical Services 60, no. 3 (2016): 140-155.