syncStateConfirmed property
Whether the other sync fields are an engine reading rather than a recorded estimate. True when the primary answered what it is enforcing, including when that answer contradicted the record, in which case the contradicted values are replaced by the ones the engine reports. False when the reading could not be taken: the probe did not answer, there was no engine to ask, or the values describe a configuration change just applied rather than anything measured. Absent when no engine was asked at all, so an unprobed database is distinguishable from an unconfirmed one. False never means a standby was found lagging, because it is the absence of a reading rather than a negative one, so draw no conclusion about replication health from it or from a response that omits it.
Implementation
final bool? syncStateConfirmed;