The minWireVersion of an RSM is computed as the min of the minWireVersion of all servers in the replica set. Similarly, the maxWireVersion of an RSM is the the max of the maxWireVersion of all servers in the replica set. By default, a server with unknown server description is given minWireVersion and maxWireVersion of 0. In a StreamableRSM, a server is assigned unknown server description when the RSM has just been initiated and whenever there is failed isMaster response. So such servers should be excluded from the minWireVersion and maxWireVersion computation, just like what the ScanningRSM does.