So your typical coffee shop has router capability to determine a quic tunnel over udp/443 vs a WireGuard tunnel over UDP/443?
I would say they disable it deliberately to prevent VPN tunneling, its probably a sane decision to disable anything not needed for the intended purpose (or not putting effort in enabling it).
They are not sophisticated, they just do not want people leeching large amounts of data via the connection (which they basically perceive as http/1 or http/2).
Anyone using "something else" is basically noise.