I’ve lived with quite a few different cats in my day. It’s simply the individual cat. Some cats overeat if allowed, some don’t. It’s certainly nice when you have one that doesn’t, but it’s nothing you did if you have one that does.
We definitely can't leave any extra food out with this one around, likewise she will try to get to people food if human backs are turned. She's calmed down a bit though, it no longer seems that she's constantly plotting how to get extra food.
So just leaving some bowls out didn't really work for them, they'd constantly eat each others' food or eat everything as quick as possible to keep it from the other cats, with predictable (and gross) results.
We got feeder bowls that only open with the right RFID and now they're all much happier and more food secure. Sadly there's no good ones on the market I could find that do both automatic feeding and the rfid-gating, so we still have to manually feed them but for the most part they don't care when we feed them anymore except sometimes in the morning (which is the most likely time for them to run out of food).
But even without worrying about eating too much, my cat definitely craves novelty and plays a lot. So I think the vet was recommending it for both reasons. He was getting too attached to going outside a lot, which I also had to curb (perhaps related).