In the new update, NPC names will appear all the time, even through walls. Previously, NPC names worked more like name-tagged mobs where they would appear when you looked at an NPC. Now they work more like player names. This change wasn't listed in the changelog, so I can only assume it's a bug. This happens in both single-player and realms. I haven't tested on servers yet, nor do I have the ability to do so. This issue affects at least Windows and mobile and could affect more.