Wireguard is a tunneling protocol. Netcat lets you write things over a socket. But netcat doesn't implement mechanisms for guaranteeing that all your packets arrive over UDP mode, so you're forced to tunnel TCP over UDP for reliability.

QUIC is all UDP, handling the encryption, resending lost packets, and reordering packets if they arrive out of order. The whole point of QUIC is to make it so you can get files transferred quickly.

WireGuard doesn't know the data you're sending, and netcat+TCP is stuck with the limitations of every packet needing to be sent and acknowledged sequentially.