/summon minecraft:goat -5.17 102.00 33.92

{NoAI:True,Rotation:[270f,0f]}

/summon minecraft:goat -5.17 102.00 33.92

{NoAI:True,Rotation:[180f,0f]}

/summon minecraft:goat -5.17 102.00 33.92

{NoAI:True,Rotation:[90f,0f]}

'

 
This will result in three goats who are barely rotated from each other, rather than 90º apart.

Also, if you summon a different mob next to the goat at rotation 180, it will be pointed in roughly the opposite direction – the 180.0f rotation is pretty much ignored, really. And the summoned goat is not pointing along an axis, but nearby one.

All in all, rotation on a summoned goat is broken.