Hi, thanks for the report. This is good news that it does work on the SGB, although it's strange that it's detected as a DMG. The machine detection code is based on the memory value after bios boot, so the Flashcart firmware is maybe doing something here.
Could you please try again with the ROM file "gbcorp_full_nolink.gb " ? This version has the link-cable feature disabled for better compatibility with some Flashcart, maybe it'll help with yours too?