Perfect forward secrecy (PFS) must be explicitly enabled with proper algorithm support in TLS. QUIC provides PFS, but only after the connection setup, and the key for the initial authentication and key exchange is not connection-specific, but is regenerated every couple of minutes. This setup is not perfect but permits QUIC to avoid one RTT and as long as the interval between key regeneration is not long it can be considered secure.
***minimaLT perfect forward secrecy is not per-connection, and requires server and dns collaboration. See the MinimaLT page for details.