Well, it could mean that mental health professionals push exercise significantly more as a treatment. A lot of people see psychologists and doctors about mental health.
They already do .. badly. There was an excellent thread on twitter the other day along the lines of "I went to my doctor saying I was suicidal and got sent away with this worksheet" - a whole collection of completely inadequate responses to acute mental health issues.
That would be the "fuck if I can help you" non-response. Around here it happens a lot because it takes so long to get into a psychiatrist that unless you admit to suicidal ideation, intent and a plan, you're not going to get help fast. A lot of family docs have their hands tied.
In practice, it probably just adds a bit more motivation or reinforcement to the existing body of knowledge. There is a lot of conflicting info out there about how much is needed, what kind, etc., so the fact that this is saying a broad range of activities and so on were shown helpful is a plus. Helps take the "should I run or bike or weight lift or... screw it, I'm sitting on the couch" out of it.