So this is a userspace app that reconstitutes the VPN encapsulated datagrams into outgoing networking socket API calls, a bit like slirp in ye olde days? I can't imagine this process is very lossless, does it really properly handle multicast, ipv6, protocols other than tcp and udp, etc?
edit: apparently, the Android VPN is flexible enough that they can direct only DNS traffic through this process, which mitigates it quite a bit. This issue has some tech details: https://github.com/julian-klode/dns66/issues/193