Yes, there are instances where it will automatically detect it but if you import a platform as say Neo Geo or CPS3, then checking that box will use the MAME import rules for a different platform name.
IF you named it Neo Geo and used MAME as the emulator than the checkbox for use MAME metadata wouldn't appear also I don't think it would find any results but I will test it myself as soon as my latest platform is done importing.