MC-173878 may be related, but I don't think it is a duplicate issue. It describes an intended behavior that can be observed on both clients and servers. This issue, however, represents a discrepancy between server and client behavior.
This issue was observed on a vanilla server and also verified using a vanilla client. I only used a modded client because it is easier to see the biome borders using modded than by using the F3 screen. However, I will add screenshots from vanilla in a bit to prove it.
Matthew Partington
MC-173878 may be related, but I don't think it is a duplicate issue. It describes an intended behavior that can be observed on both clients and servers. This issue, however, represents a discrepancy between server and client behavior.