http://ciisqbg45nggykdl6rjdrq3wc64csga4vkphu66qsi65mypeitqedoad.onion/blog/multihopping-wireguard
To prevent that theoretical situation from happening, you could always combine this type of multihop with another VPN provider that supports WireGuard. Connecting to them before us would mean we can't get your real IP, but we can see your outgoing traffic (which should be encrypted, so only the metadata), and they can get your real IP but not see your outgoing traffic.