Originally Posted by
awair
Typically because in the event of an interruption in the process, like making or receiving a radio call, the switcher forgets to return tuning to the appropriate side. Now the offside tuning light remains illuminated, and no-one knows (immediately) why.
Conversely the offside tuning technique might be used if the the PF (helpfully?) tunes a new frequency while the PM uses the transmit switch on their side Audio Control Panel...
I see. You’re talking about a temporary use. I was envisioning a scenario where the FO would just keep his panel on com 1 (assuming all ATC transmissions are on com 1).