In 1.480.3 if you create an external monitor job, and do three builds, then go the the latest (#3), you will see a Previous Build link as expected. But in newer cores you will not see this link, even though all three builds appear in Build History.

The reason is that there is nothing actually writing to the previousBuild or nextBuild fields, contrary to their Javadoc: RunMap does not touch them. (dropLinks would update them after deleting a build, if they were not null to begin with, but they are.)