What does "on coming out" mean?

"On" means "about." "Coming out" is in reference to the idiom "in the closet" meaning homosexuals that for one reason or another hide their sexuality. The article is about an openly gay men's college basketball player talking about being open about his sexuality. It's a redundant sentence.

So "on coming out" mean "about to reveal his true sexual orientation"?

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So "on coming out" mean "about to reveal his true sexual orientation"?

Not exactly. "About to reveal" means he still has to do it. (It hasn't happened yet)

"...on coming out...", means he is writing about what it means to disclose his homosexuality.

nobody comes out as a heterosexual.

Exactly, nobody comes out as a heterosexual.

Disagree.
If you "come out", you are talking about homosexuality.
If you "come out" as an alcoholic, a trainspotter or a conservative, you need to explain what you are explaining.

Anatomical analysis will be appreciated.

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Anatomical analysis will be appreciated.

Could you please explain what you mean by this?

By extension it can now mean to reveal a number of things, not necessarily connected with sexuality. I recently came out to my colleagues as a trainspotter. People might talk about coming out as an alcoholic, a conservative or an atheist for example.

The word "anatomical" is related to "anatomy" as in physical body parts. Medical students study "anatomy" where they learn the names of all the bones, muscles and organs.

We use the phrase "anatomically correct doll" to mean a doll that has genitals.

Usually when I use the word "anatomical" it is as a somewhat joking euphemism for genitals. Which is why when I read your post, the first thing I thought is that you wanted me to look at your penis.
I (as a native English speaking American) have never used the word "anatomizing". In fact, I had to look it up to find out what you were talking about.