Well yeah ofc the camera feed goes thru the Internet so you can view it from anywhere?
I suppose they could bang a hole out thru your router & host something on the printer, then have your app sync your ip when on the wifi with the printer, but then if your ip changes when out & about you'll lose access unless you've set something up for it.
Gotta remember that Bambu is all about ease of use. It does have a LAN only mode, but I do agree that they should support some sort of plugin system for the printers and just refuse to support unless you're experiencing an issue while using 0 modifications/plugins.
Maybe last year people were saying that Bambu intercepts your models, that it's not private.
As I google, they say that your camera feed also goes to the public internet.