right, either the BUTTON1 shouldn't fall through to the emulation if clickable artwork was pressed (usual UI keys fall through to emulation issue?) or MAME shouldn't be mapping mouse buttons to inputs on systems with clickable artwork in the first place.
still, it's an understandable confusion as it seems logical to specify -mouse if you plan on using one, even if in this case you don't have to, and doing so is harmful.
