There's a bit about the port as a section of a longer discussion about publisher Firebird: https://youtu.be/LWHJomIX_As?feature=shared&t=2297 . Which does state that yep, it was mostly made by playing the arcade game lots then doing the best they could. They apparently did have some documentation... in Japanese.

AFAIK "here's an arcade PCB, write this for the C64 / Speccy" wasn't an uncommon thing back then. Arcade perfect wasn't really a thing for the 8 bit micros...