Correct, map filters do affect auto-collection, I should add a clarification indeed!
It would not work any other way, unfortunately, as when any item/resource/character is filtered out, it simply isn't loaded from the server and the app doesn't know about their existence (so cannot trigger collection due to proximity). The server does not actively monitor your position either (that would be an overkill and a potential privacy concern), so cannot trigger automated collections as well.
And pre-loading all data in the client regardless of filters (but just not showing it) would consume more traffic and memory, which as you've correctly pointed out is one of the reasons older devices use filters in the first place.
Yep, if the GPS is available you should be able to turn off internet connection and use offline captures.
Every situation and device are different, but that's the general idea. 🙂
I tested this functionality on a ship not too long myself and it worked (with varying accuracy, of course, but still completely without using any mobile data).
Regarding the status bar: thank you for noticing and letting me know, I did not see that!
Will add it to the list of things to address.