Cages (iron bars) get created on small obsidian pillars which causes them to overlap the pillar. In previous versions (for example 16w06a) they were generated on the big pillars.
Use the following seed ("Default" world) and go to the End
The following is based on decompiled version of Minecraft 1.9 using MCP 9.24 beta.
The reason why this happens is very likely that in Minecraft 16w06a the method net.minecraft.world.biome.BiomeEndDecorator.SpikeCacheLoader.load(Long) determined whether to create a cage using boolean flag = l > 5 whereas in Minecraft 1.9 it uses boolean flag = l == 1 || l == 2.