I'm aware of the trope. I've yet to meet anyone that adheres to it, though. Always thought it was just one of those things that Hollywood overemphasizes to "other" gay people.
GP linked you to a summary of a scientif finding, not a trope. You can read more about the study here [0].
Regardless, I think the point of collecting these stats is to make sure voices of people that might normally be under-represented in a uniform sample of a relatively small size can be corrected for. These are common stats to collect in surveys for similar reasons.
There was someone in my high school who had the stereotypical voice. One of his friends, who'd known him since they were little, mentioned that he had talked like that his whole life.
How does being gay change your voice?