Yes, it will then be routed through the VPN (logged out the INET type of the packets to verify). So the behaviour is what can be expected, either the traffic goes through the VPN or the app(s) won't get any traffic through at all (as opposed to the destination IP mode which let traffic go outside the VPN if one doesn't setup the NEIPvX settings). Thanks for your time!

Thanks for your reply. I cannot test binding on the macOS side since it is an iOS/iPadOS only app (what I know of, until silicon I guess :) ). I guess I could bind manually in a test-app though.. I tested it with and without settings for v6, and without it the app doesn't get internet (when using a ipv6-only address). So I tested without settings for v4 as well (so we don't get any traffic at all), and then the app(s) got no internet connection at all. So it seems that a Per-App VPN forces the traffic through, and if we don't register for packets/traffic the app(s) won't get internet.