it stops you from using certain updates such as 1.9 an up including 1.9 snapshots

what the bug is is whenever you change the update from 16w14 to 1.8.9 for a server but then once you try to get back on to latest version it wont allow you to so you are then stuck in that update (it happened to me an 1.10 just started and i'm still in 1.8.9)