No, there are almost never good ethical reasons to be concerned about this. Study after study has shown that medical transition leads to positive outcomes for the vast majority of those experiencing gender dysphoria, and that most negative outcomes are better attributed to societal stigma and marginalization of trans people. After all, it does not matter if your transition went well if you still live in a society that continually denies your personhood. As with any medical procedure, there are risks involved in transitioning, though these are often exaggerated, especially in the case of hormone replacement therapy.
Chemotherapy is a literal poison, yet we still use it, because through rigorous testing and the scientific method, we have determined that the benefits outweigh the drawbacks for most patients. There are exceptions in these cases, of course, but there is a reason your list of de-transitioners includes only a handful—they are the minority. Again, there will always be people dissatisfied with the results of their treatment; or even worse-off because of it, and doctors are trained to ensure their patient is made aware of these risks before proceeding. This is an unavoidable reality of medicine, not evidence of some taboo against “allowing” discussion.
The fact that this almost exclusively gets talked about when it comes to transition is precisely why most people don’t take this line of reasoning seriously. Most accept this medical reality when it comes to virtually any other treatment, which is a major reason why people who claim to be “expressing concern” are rarely interested in helping anyone. If they were, they would have already engaged with the evidence that challenges their worldview. I know, because I used to be one of them.
With that being said, this isn’t the place to be having this debate to begin with, but I also in good conscience couldn’t leave this without a response, trying to frame DHHs statement as “legitimate concern” is ridiculous.