Causal and session are definitely similar, but I'm not entirely sure if causal implies consistent prefix, and conversely, I think causal miiight have stronger implications than just the intersection of MR, MW, RYW, and WFR. Because we weren't entirely certain whether we could make that claim regarding Cosmos, we opted to be conservative.
I agree it's hard for me too to be precise about naming in academic sense. But this published paper "Writes: the dirty secret of causal consistency" says that both Cosmos DB and MongoDB have causal consistency so I don't know.. At least Cosmos DB and MongoDB provide the same guarantees for session/causal.
