From looking at the HomeKit accessory protocol documentation under stream management, 30fps is only the minimum "recommended" frame rate for streaming. The minimum supported is actually 24fps.

I don't know if this lower supported minimum would make much difference in heat though. Maybe Netatmo should be using a chipset that has a lower thermal draw.

Here's what a teardown of their doorbell looks like https://fccid.io/N3A-NDB01/Internal-Photos/Internal-Photo-pd...