I'm guessing they're referring to conflicting transitive dependencies. Everything works fine when you use version 1 on date A. A couple years down the road, all those depends have matured at different rates and the top level packages all specify different versions of the same transitive packages so you have to try to line them all up.

On the other hand, the longer you wait to update, the worse it gets. Updating more frequently you can suss out packages moving quickly vs slowly vs not at all and address the problem before you're in update paralysis