Regarding your scan question, it is not clear what you are asking. I think I might know what you are referring to so I'll give this a shot.
In CPS and scan setup, you have the ability to indicate what channel the radio will talk on when in scanning mode. The radio can be setup to transmit only on the main selected channel (what channel is indicated before you turned scan on). The radio can otherwise be set to transmit on the active receiving channel during scanning - meaning that if you talkback on that active channel (or talk group) which is different than what your main selected channel is (if you turned the scan off). This setup has its benefits but also its drawbacks.
Let's say you turn on the radio and it powers up to channel 1. You begin scanning. If you key up the radio while the radio is scanning your selected group, you will be calling out on channel 1. Now lets say that a QSO comes up on your channel 5. The radio will allow you to talk back on channel 5. However depending on the timing settings of your radio setup, the radio might release that active channel and you could end up transmitting back on channel 1 even though your original conversation was on channel 5. Conversely the same can happen if you are trying to talk on channel 1 but a new QSO comes up on channel 5 and the radio might inadvertently switch your selected TX channel to 5 even though you want to be on channel 1. So to help avoid confusion and be courteous to others I believe you are being told to slave your TX to the main selected channel, and not what channel the scanning stops on.
I don't think this prohibits you from still having or creating a mixed zone channel or talk group scanning profile. As far as I know you can still add or select any channel in your radio to be in the scan group that is programmed for that specific channel personality. But don't quote me on that because I have not played with that to any great deal. I primarily use my radio for TRBO only and only have two zones (system and simplex).
Hope that makes sense.