When an RS member is in a primary/secondary state, direct connection to it appears to claim that the server is OTHER. As far as I can tell the server should be in the same state as it would have been had the driver connected to it as part of RS topology.

Besides potentially interfering with background thread starting logic for connection pools, this also has the consequence that the driver believes 3.6+ servers to not support sessions when such servers are RS members and the driver uses a direct connection to them.