 If it's a good tile job where the grout looks perfect or the tile's sitting right there with a real thin grout line, that's all good. If you've got gaps or something and maybe that tile job wasn't so good, a bead of silicone might look pretty nice there just to kind of finish it off. But no, there doesn't really need to be anything there down the road. If he hasn't sealed the grout, that's probably a good little insurance policy for you.