why do some people get T voice and others don't?

Firstly this will come across as quite humblebraggy but I don't mean for it too, I have plenty of things about my body that I love to criticize as clocky, this is just one rare thing that happened to go well for me.

90% of trans men I see have t voice. It's not absolutely everyone, but it's the vast majority. It's possible this is due to selection bias, where more trans men don't have T voice but they pass as cis men so we don't clock them. I remember pre t expressing my worry over developing this to my therapist, who had seen hundreds of trans patients as he was one of the few therapists in my area who wrote hormone letters.

He was a cis man and he agreed to me without hesitation and in full confidence that he'd literally never seen a patient return to therapy post T with a deep voice, they were always high and nasally. He told me it's something i'd have to prepare for, as even if I avoided the T voice quality, i'd certainly not have a deep male voice, perhaps just medium or high one.

Strangely, when I went on T my voice proceeded to drop very quickly and I developed a visible adams apple. I went on T at 19, my puberty was well and truly complete by then, my bone structure otherwise did not change at all (still stuck with teeny hands and feet) and my T levels were actually a half dose at that time at the suggestion of my endocrynologist who wanted to gradually ramp up my dosage levels.

I would post a voice message but I'm stealth irl and can't risk being clocked, but my voice not only does not have that T voice nasal quality to it whatsoever, but it's distinctly lower and fuller than most of my male relatives, it's not even a baritone it's a bass. I'm extremely grateful for my voice, it's what allows me to be stealth because I otherwise don't look completely cis passing, but I am so confounded as to why this worked for me but rarely ever works for other trans men. The only other trans man I know with an adams apple is Jamie Dodger and while he sounds normal, his voice isn't really low.

I didn't do anything different to other trans men as far as I know when going on HRT and I never voice trained, not even once. How come this worked for me but it never happens for others? Is it really just genetics? My family don't even have particularly low voices.