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.
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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.