It looks like you are talking about the auto-refill option available to anyone with an AMS. If you are, this still needs to purge the existing spool.
The OP is trying to work out a specific case with the auto-refill function, do you have to wait for the auto-purge or can you “pretend” the manually replaced filament is still part of the original filament by standing over the printer and chasing the old filament with the new. Make sure not to lose tension as it goes.
I believe you are talking about the very same thing,
One caveat for you though - the checks on filament type do not occur during the print process, thus, you should be able to swap one spool out for another without the process failing. The auto-purge will continue, and the new spool will be pulled in.