Villages merge (in spawn chunks)

When I create different villages in the spawn chunks and reduce there distance to a minimum, these villages were supposed to stay different because the chunks stay loaded.

This only works up to version 15w35e (see first attachment). When I open the save-file in every newer snapshot, the villages merge immediately into one single village (see second/third attachment).

Remark: For the screenshots I only used one mod to show the boundaries of the village(s).

I don't know if this is intended behavior (bugfix?), but I've found nothing about it in the change logs.
It will break iron-farms like The Iron Titan by Tango Tek.