If you were to attempt to place wither skeleton skulls with a dispenser, they would only place if the the soul sand/soul soil blocks are horizontal

Steps To Reproduce:

1. Set up the "T" of soul sand to sumon the wither

2. Place dispensers facing the blocks where the skulls would be placed and put wither skulls in them

3. Activate one or more of the dispensers. It does not matter if heads are placed or not, they would be dispensed as if you were using a dropper

Observed Results:

The Wither Skulls are dropped as items rather than placed

Expected Results:

The Wither skulls would be placed and allow the wither to be spawned