Lock your camera in the general settings if you want a more predictable behaviour (but you’ll have to change it manually before each render, once locked.).
The button on the VFB is identical to the max’s function “render last”, so it behaves exactly like that (or the F9 key.).
I’m not sure why it wouldn’t render the camera you set in the render settings.
It’s as quirky as max’s command is, no more, no less.