It'd be easy to check. It was true on my 1998 Mercury Mountaineer, I can't imagine car manufacturers would go back just for funsies.

I've personally experienced it on at least six different car infotainment systems by four different manufacturers where the stereo will start playing whatever was left on, you turn the volume knob but the whole thing is still loading so it doesn't react for a few seconds.

Even outside of OEM head units, I've owned a few after market head unit stereos where the volume knob was technically a digital input and if the system was lagging hard the volume input could be delayed a good bit.

A number of these systems will have a different volume level for things like phone calls than for the music, but both volume levels are controlled by the knob. It'll also do things like automatically lower the volume level for notifications or have dynamic volume levels based on acceleration. The knob is rarely directly controlling the actual output of the system.

Here's a good question: if you press the volume buttons on the steering wheel controls, does the volume knob on the radio move?