Before PV1 (and terms), we used election id to determine between two primaries, which one is more recent. We started returning electionID in the hello command so that drivers could learn about more recent primaries by looking at electionID. When moving to PV1 and using terms instead of election IDs, we never changed what we send to hello. We just started generating election IDs in a special way (with the timestamp portion being set to the max timestamp) so that an election ID created from a higher term always compares as larger than the election ID created from a lower term.

This code is confusing and unnecessary, so we should replace election ID with term. Note that doing this ticket does come with some concerns around communication for mixed binary sets and has large implications on SDAM.