It seems like this part of the documentation was not updated after changing the default value of recovery_target_timeline to latest in v12.
"The default behavior of recovery is to recover along the same timeline that was current when the base backup was taken. If you wish to recover into some child timeline (that is, you want to return to some state that was itself generated after a recovery attempt), you need to specify the target timeline ID in recovery_target_timeline. You cannot recover into timelines that branched off earlier than the base backup." [1][2]
