The SCTP mapping excludes using a new stream of an already existing SCTP association on Initiate when activeReadBeforeSend is used. This is about the (unusual) pattern where the client opens and then reads without first sending anything. In SCTP, the server can't learn about the creation of a new stream unless the client sends data on it, so such stream mapping wouldn't work.

Is this different in QUIC? If yes, we must say how (because the general approach is to just send data). If not, we must also exclude using a new stream of an already existing connection when activeReadBeforeSend is used ("Preferred or Required").