Upside down stairs behave in a strange way in 15w38b

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I am working on a custom map, and I noticed Minecraft 1.9 is almost out (I saw a video on YouTube about 1.9). I thought those additions could be very useful in my map, especially those new command blocks and the cooldown on weapons. So I started Minecraft on the latest Snapshot (15w38b) and I started working on my world again.

The first thing I noticed is that the shape of my upside down stairs (for decoration I added upside down stone brick stairs) was wrong. It took some time to discover what was wrong with the shape:

shape: inner_right should be shape: inner_left,
shape: inner_left should be shape: inner_right,
shape: outer_right should be shape: outer_left,
shape: outer_left should be shape: outer_right.

Note: this is not the case for stairs with half: bottom (regular stairs), only for stairs with half: top (upside down stairs).
It is the same for other types of stairs.