Hmm, if that were the case, wouldn't the time spent waiting be variable? That would mean that you'd sometimes get instant switches, when the I-frame was the next frame you received after the switch.

It is variable, the stations are multiplexed on channels, so sometimes you can use the same stream and sometimes you have to switch. That takes time.

I presume the TV hides that by always taking the same amount of time to change stations.