The following is the rules for topologyVersion comparison

1. If the response topologyVersion is unset or the ServerDescription's topologyVersion is null, the client MUST assume the response is more recent.
2. If the response's topologyVersion.processId is not equal to the ServerDescription's, the client MUST assume the response is more recent.
3. If the response's topologyVersion.processId is equal to the ServerDescription's, the client MUST use the counter field to determine which topologyVersion is more recent.

Point 1 is not correctly checked by our driver:

const topologyVersionsEqual =
      this.topologyVersion === other?.topologyVersion ||
      compareTopologyVersion(this.topologyVersion, other?.topologyVersion) === 0;

Here, if both topologyVersions are null we'll true for equality when actually other should always be greater. Fixing this causes a spec test to fail:

Monitoring a direct connection - suppress update events for equal server descriptions

Extra events are emitted because now the serverDescription changes with nullish topologyVersions are considered different