I've moved into a new home and some water is leaking due to incomplete grouting of tiled walls in shower. Shower has pre-made shower pan, not tiled floor. Builder has cleaned out (by drilling) small weep holes in tiled wall immediately above pre-made shower pan (shower floor)... like you would see on exterior brick wall at lug level - to let any water flow back into shower floor, and then dry out. I know of weep holes in the shower drain... but are there supposed to be weep holes in the tiled wall just above the pre-cast shower pan??

No, If Your Getting Water Back Behind The Wall Your Asking For Problems In The Future With Rott Your Not Going To See Till Its To Late.
Make Sure You Don't Have A Leak In Your Pipes First, Go Under The House And Check To See Any Water Or Moisture Build Up

When The Tile Is Installed There Needs To Be Durock It's a Concrete Board All The Seams Need To Be Sealed Also.
There Shouldn't Be Anyway For Water To Get Back Behind The Tile Wall.
Now With That Said, The Grout Joint Shouldn't Be More Than 3/16 To 1/16 Wide The Ground Unless It Is Sealed Will Let Water Past, But Not To Where You'll Need A Hole For It To Come Out.

If There Is No Durock Behind The Tile, You Will Have Rotten Studs And Eventually A Floor To Replace In Time.
Hope This Helps , Nichols Trim And Carpentry