Don't agree. Health wise I am of the opinion that it is probably unhealthy to exercise say 10 times a year. Your heart just isn't used to it. You are supposed to build up slowly and regularly. Again don't agree with the mental health suggestion. Simply not often enough. Remember I said summer only and when the weather is just right. I assume weekends only. I think they are called weekend warriors. Met one once going down a steep hill he was coming up. Said to me "it is easier cycling down than up". His girlfriend said the same. Half wits. Wouldn't mind but they were walking up the hill!
It's still exercise and still possibly more than they normally do. And some get the bug and continue. I was a once a year cyclist who did the hire the bike and cycle along a cycle path annually on holiday. Yes I wasn't fit, but neither did I need to see a doc before I attempted it. If you go out 10 times a year then you tend to take it easier than the regular cyclists. I've gone out on a ride with friends who don't cycle regularly, and you just need to lower your speed considerably and take into account that they might want to stop quite frequently. Not make a big issue over it. The last ride with friends one ended up turning back after 2 miles and I felt really bad that he didn't think that we wouldn't be happy to adjust to his speed. I don't mind I just see it as a social.
My main concern about the new cyclists is their road awareness and not thinking that the highway code applies to them on a bike (whereas if they were in the car then it would apply to the cyclists they see). And a lift in mental health however temporary has to be a good thing too.