This study seems to me to be a retreading of old ground by cis people. Like I can appreciate getting more data that yes, trans people aren't freaks, but the study just seems like a massive "duh".
Why did they think hrt changed vocal chords in trans women in the first place? It's pretty well known that hrt cannot take away the things that first puberty already changed. I also don't like how the article presents voice feminization surgery as if it's a common and normal choice for most trans women. Even beyond the implication that trans people need surgery to be successful in their transition, voice feminization surgery is extremely risky and is only ever recommended in extreme cases. If they couldn't even do that amount of research, it doesn't make me feel confident that the study is all that worthwhile to think about.
Secondly, why only focus on trans women? It'd be more interesting if they included trans men in the picture since on their side of the fence, hrt actually does affect their voice. It would be interesting if the study compared their trans participants with cis benchmarks at all, actually. Maybe the study itself does that where the article does not, but for reason #1 I don't feel like it's worth my time to check.
Lastly, the actual results of the study are pretty "duh". Just by the physics of how the human voice works, it's pretty easy to see that yes, having a breathier and higher pitched voice will lead to having thinner vocal folds. Because having thinner vocal folds is what causes those effects on the voice in the first place. The study mixes up the cause and effect here, so it isn't exactly groundbreaking research. What would've been more appropriate to examine is the vocal chords at rest compared to either cis benchmarks or the speaking voice average. Since the conventional wisdom is that voice training can't really change your voice at rest, that would be more interesting to look at.
Overally I appreciate having more data about trans people, but didn't find the study or article to be particularly knowledgeable about trans people in the first place.