Is this a thing? My quick search isn't showing anything like that, the closest is the butter container, which is designed to be a bit warmer than the rest of the fridge. There's no heat element involved though.

This seems to be a thing that has changed or is changing.

“Butter conditioners: These used to be a standard feature of New Zealand fridges, but they seem to have gone the way of the dinosaurs. We think that’s a good thing. Butter conditioners lower a fridge’s energy efficiency, and they don’t necessarily keep butter at a useful temperature anyway. If you want to keep butter a bit warmer, use the dairy compartment in the door.”

https://www.consumer.org.nz/products/fridges/guide

Huh, it seems to have mostly been a thing in the UK, Australia, and New Zealand. That'd explain why I've never heard of it, in the US we only had the compartment.