Additionally, I expect this node will not behave correctly at the P2P layer. v2 onions were “inserted” into Bitcoin by reusing some address space within IPv6. v3 onions are far too large to do this, and I have not checked what the P2P layer will do when seeing them, but I expect it will involve truncation. My open ticket for I2P integration will also enable proper v3 HS support.
EDIT: I have looked at the source code, and what happens is that a lookup of a v3 .onion will be ignored by the regular onion-handling code (as it is too long), and will instead be passed to the DNS lookup code (treated as a hostname). I haven’t been able to figure out exactly what happens after that (as it partly depends on what gets returned to the lookup code by Tor, assuming that is set properly), but suffice to say that if it does work currently, that is only because the -addnode entries are being passed directly to Tor’s SOCKS proxy port. Discovery via the P2P network is definitely non-working, and internal detection of these addresses as Tor addresses is definitely non-working.