The texture of Smooth Quartz is the side texture of normal Quartz (that looks like tiles), not Smooth Quartz.
I personally recommend adding a new block called Quartz Tile with the current Smooth Quartz texture, and changing Smooth Quartz's texture to the actual smooth (underside of normal Quartz block) texture.
Environment
Microsoft Windows 10 Enterprise x64 Portuguese (Portugal), Java version unknown (it's whatever the official Minecraft launcher installs on its own), Intel Pentium Dual-Core E5700 @ 3.0 GHz, 4 GB RAM, AMD Radeon HD 5450 with 1 GB video RAM.
Linked issues
Comments 4
The name is consistent with the other blocks that do the same: top texture of slab variant on all sides.
Smooth XXX uses the top texture of the slabs on all sides, that’s exactly as Smooth Quartz does.