Android is pretty liberal with backgrounding relative to iOS. It's iOS that needs notifications to do anything meaningful in the background.
I suspect Android lets these sockets stay open as long as they're for something specific - in this case it looks like WebRTC might be allowed so they "munge" the cookie in:
The Meta Pixel script sends the _fbp cookie to the native Instagram or Facebook app via WebRTC (STUN) SDP Munging.
Android is pretty liberal with backgrounding relative to iOS. It's iOS that needs notifications to do anything meaningful in the background.
I suspect Android lets these sockets stay open as long as they're for something specific - in this case it looks like WebRTC might be allowed so they "munge" the cookie in: