First, I believe mental health is a real and important issue where the military (and society in general) needs to do a lot better than they are.
But if someone has mental health issues so early in their career that they miss out on a significant part of their initial sea tour and qualification process, what makes you think this won’t be a continuing issue throughout their career? If so, it should be a medically disqualifying issue like any other chronic issue that affects your ability to do the job.
If the mental health issue is treatable without affecting their job, then they should be able to continue in that job.
The career reset doesn’t happen with any other health issue. If you want mental health to not have a stigma attached, then you need to treat it the same as any other health issue.