Look up cluster feeding.
parenting
A welcoming place for all parents to give advice and share their challenges.
It's basically impossible to overfeed an infant. Like you say, they mostly know when to stop, and they'll just spit up whatever they can't handle.
My baby will get extra hungry and sleep extra long when they're going through a growth spurt.
I'm not a doctor, and maybe someone else will say it's bad... But for what it's worth we also let our infant eat until they think they're done. Sometimes is an incredible amount of food... Like as much as I'd eat for the meal.
We try to restrict eating to mealtimes, though. Again, not a doctor, but we don't want him to think eating is just something you do when you're bored
Also not a physician, but I'd say I'd agree as long as it's not ultraprocessed food they're eating more of - food which is designed to hack your innate pleasure responses.
The thing to remember though is all that growing children do is literally made from the food they eat. They need to eat a lot to grow, and calorie restriction can drastically impact development and long term health outcomes. There's lots of research on that in children post-famine.