Letting the silicone dry on the tile may pose a problem for clean-up. This is if one was to apply sealer after the grout was layed. As for applying grout with the silicone already in it, I too, have had no problems related to it. It simply gets wiped off as part of the install. But, again, in the 1st scenario, you want to wipe off the stand-alone sealer before it hardens on the tile.