I think it's true; I think mental health information finds its way into pre-sentence reports, but finds its way into them on consent. Defence counsel will tell their client that this is something to tell the probation officer, or the probation officer may be alive to it.
Adding it as something that is mandatory, that has to be in the report, however, makes the case very different. Now it's a sort of voluntary thing that could be put in, but putting it into the code would make it something that has to be put into the report.