You'd have a tough time getting grout to be flush with the surface of the tiles. Grout will be wiped off slightly below the surface with the sponge. It's also desirable to expose the chiseled edges for appearance.
Having said that, although that tile is very dramatic, it's going to be a nightmare to maintain in the typical shower. You sure you want that?
TILE GUY - retired- TROY, MI - Method & Product suitability consulting.
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