seamless double sandstone slabs have the texture of seamless double stone slabs

Put the summary of the bug you're having here

What I expected to happen was...:
it would appear as a seamless double sandstone slab

What actually happened was...:
it appeared as a seamless double stone slab

Steps to Reproduce:
1. type /setblock ~ ~ ~ minecraft:double_stone-slab 9
2. this should be a seamless double sandstone slab