It used to turn them off on the iPhone, but not these days.

A lot of planes have WiFi, and people are also using Bluetooth headphones. So when talking about being a passenger on an airplane, this seems like a rather practical choice.

Not for my Android phone, at least not by default (Pixel 9a a/ GrapheneOS). It leaves Bluetooth and WiFi on in airplane mode. I doubt this is specific to GrapheneOS and may say more about AOSP.

That's a setting you can tweak with various software.

Not if you were connected to either when turning on airplane mode. Both can also be turned on manually in airplane mode. A physical block avoids any uncertainty or mistakes.