The opposite happened to me when I transitioned. When I was perceived as a guy, if I was in a meeting, people didn't instantly fall silent if I spoke, but if they tried to overtalk me and I just kept speaking, they would eventually give way. I transitioned 8 years ago, and from the earliest days of my transition until now, if someone starts overtalking me, they will just keep doing it even if I don't stop talking. The only way to stop them is to vocally call them out and ask them to be quiet until I'm finished.

Similarly, I used to be seen as one of the two "tech guys". The person that people would come up to and ask for tech advice to avoid calling the internal helpdesk. After I transitioned, they started coming up to me and asking me where the other tech guy is.

My career has stalled since I came out. I'm in a trans inclusive country, in a trans inclusive workplace, and I transitioned so long ago, that most people don't know that I'm trans or simply forget. But since coming out, the various shoulder taps in to project opportunities and the like just don't happen anymore.

Maybe people went silent because they were fascinated by or fixated on the unusual timbre of the OP’s transitioned vocal cords.

It's a nice theory, but it's somewhat strange how my own experience as a trans person transitioning from male to female had the opposite impact. Did people start overtalking me because they were fascinated by my timbre?

Additionally, OP was in the same department for years and then transitioned. So, naturally people would approach a more experienced person for help or advice regardless of perceived sex if they knew that person was there longer than them.

Again, it's a nice theory, but in my case, they stopped approaching me. And even the ones who don't know that I'm trans don't approach me that way, because I'm not seen as one of the "tech folk" anymore, despite not losing my experience when I transitioned.

but OP seems to be using the worst possible anecdotes

Similarly, you are using the least likely possibilities that contradict the first hand experience of folk directly in these scenarios to fit your pre-conceived notion of what is happening.

Yeah, the OPs post and mine are anecdotal, so you shouldn't take either of our experiences as universal truths. But your takes aren't even anecdotal. They're suppositions.