No, you didn't understand what Peter was saying. He wasn't suggesting that BBC Radio 1 and BBC Radio 2 would be playing the same thing!

Radio is very different between the USA and most of Europe. In the USA most channels are broadcast with a gazillion Watts from one transmitter only. If you're in the reception area, great, if not. tough.

In the UK, many channels are broadcast nationally from many transmitters with less power. So when you travel west from Sheffield and cross the Pennines, and you lose reception from the Pontop Pike transmitter, you should pick up reception from a transmitter on the western side of the Pennines (Sanfield). Obviously reception isn't a yes/no affair - there is a zone that you will receive both signals.
If those two transmitters broadcast on the sam frequency then this would be a problem. Even if the two transmitters are frequency- and phase- locked together, as soon as you move the receiver the Doppler Effect comes into play, raising the perceived frequency of the transmitter that you are travelling toward and lowering the other. This results in 'beating' where the reception fades in and out rapidly.

To get around this, different transmitters broadcast the same program on different frequencies, so when reception from the Pentop Poke transmitter deterioates too much, you try the frequency of the Sanfield transmitter to see if the reception is better. (This is one of the things that RDS does automatically.)

So the bank concept probably originated in being able to keep two sets of frequencies for each channel, and easily being able to switch between them to change which transmitters you were listening to.

HTH.