[Enoch]

Is it actually a bolt… it looks more like a spigot like the ones above with the gears on them?

 

[Enoch]

Yup, thanks.
View attachment 57740

Any idea why the cover bolt allows access to the 6mm hex head on the end of the shaft? Is there maybe some sort of adjustment factory techs have to perform prior to certifying the engine as properly counter-balanced?

Balance shafts usually have some sort of preload that puts pressure against the opposing shaft. It’s possible that the hex is for an Allen key so that the preload could be set.