Good catch! It's not unusual that the power supplied by sources other than the shore cord have breakers not in main panel. You found the ones for the inverter supplied power. There are of course 120 v breakers on the generator and 12 v or even 120 v breakers built in to the inverter/charger itself.
I think the reason owner's manuals are so non specific is because it gives the freedom to change things 'on the fly' during assembly without having to re-write the owner's manual. The OM must be run through legal review, which can make any changes very expensive. If you look at various manuals on line, you discover they seldom change from year to year or even different models to remain as 'useful' to the manufacturer as long as possible. The number of models, layouts, lengths, etc. are far more varied than autos or trucks, making specific details less likely to be included in the manuals. Many new buyers look for details and specific locations that are just not present in them. That's what makes this forum so useful, our combined 'discoveries' can be shared to reduce the amount of sleuthing each owner has to do.