I have a 2007 Toyota Camry Hybrid that does exactly what the OP indicates. With car in park you can put the gas pedal all the way to the floor and the gas engine just sits at idle (assuming the gas engine is even running).Curious...which cars are you referring to that don't do that?
It doesn't have a tach so no gauge to look at. It doesn't have the EV/Normal/Sport selection so there's no different modes to try it in.
It does have N, but I can't recall ever trying to rev the engine while in N.