QUIC is already ~30% of HTTP traffic. That’s enough to not make UDP use stick out as suspicious.
The IP storage also doesn’t have anything to do with Tor guard nodes - in a VPN-before-Tor scenario, the guard nodes would only see the VPN server’s address, whereas in a Tor-before-VPN scenario, the VPN server would only see the exit node instead, which remains unchanged throughout the time a connection is established. If establishing a new connection instead, you have to negotiate keys for that new connection, with the previous connection’s keys not being used. The VPN server would only see connection data for the 2 exit nodes.
https://hiphish.github.io/blog/2023/10/18/grayjay-is-not-open-source/