I think there is an inaccuracy in that comment. Double check this: wire guard encapsulates L3 IP packets, not L2 Ethernet frames. This means ARP is handled locally instead of being transmitted over the wire (or the need for an arp responder)
You are right, I wrote it backwards -- WireGuard supports only IP packets, not Ethernet frames while tinc supports both. The example that I gave why Ethernet frames is more useful is correct, just the factual part is reversed.
