Thanks Chen, I think this is a bad specification.
If a user dares to choose external memory, please give priority to it.
What do you expect to happen when the user chooses external memory but it is not mounted?
It should only save to MicroSD or eMMC if external memory is selected and it is not mounted at startup.
If I were a developer, I would implement it that way.
I would like to know the true logic behind this specification.