Bomb Jack dip switch question

[lagerfeldt]

I've noticed that the Bomb Jack original arcade manual(s) as well as the dip switches shown here:
http://adb.arcadeitalia.net/dettaglio_m ... search_id=

mention the special coin (frequency) as an option to set as easy/hard or more or less frequent.

However this option is missing from Bomb Jack in MAME/MiSTer, while another option called "Bonus" at e.g. 500K can be set instead. The latter not mentioned in any of the original arcade manuals I've found.

I wonder why this is since that's quite a difference.