I disagree. An ARB dual or my superflo dual will inflate a single tire from 18 to 38 psi in about 3 minutes. But a friend of mine had a pressurized tank and I was able to inflate the same in about 30 seconds. Now, could I have done all 4 tires in 30 seconds? Maybe. If that’s the case then yes the stem would be the limiting factor. But I don’t think it is for any compressor without a pressurized tank
There’s variables
If tank is full when you start, sure, will be faster
But as air in tank depletes, it’s basically like filling a much larger tire with a lot more volume and will take longer
So first tire may be faster, but the rest would likely be slower, unless you wait for tank to fill, etc..
That @TeCKis300 engineer fella can probably explain better than me