The owner's manual is written by technical writers (Oh I might add this applies to dang near all owner's manuals) who may or may not be engineers but who are not the end users.... They sometimes forget little things like "The light runs off the battery not shore power" part.
As an engineer who specializes in technical translation (Re-writing the thing in plain language).... Well.....
It helps that I have one too.
I have several manuals I've re-written where folks say "oh that's way too hard" after reading the official manual and then they read what I write and WOW was that easy... So far I've only one manual (Icom ID-880H) where I have not been able to do that..