pics would help, but there should definitely be drainage behind the wall. What's the wall made of?

I have put in a wall and used both gravel and a 4" flexible drain pipe and it eventually fell over. That wall was not mortared. Just blocks the size of a 4" cement block stacked up. I have seen mortared walls with a bottle embedded in it. They used to break off the bottom of a glass bottle and build it in with the neck on the outside.

If I were to build a mortared wall I wouldn't use mortar mix as it's like a bag of sand. I'd use portland cement mixed myself with sand.

The minimum recommendation for behind-wall drainage depends on the height of wall and it's surcharge. For a garden wall (say <3' holding a raised bed) it is not typically needed. But for a retaining wall (>3') you would want it no matter, and want it if a 3' wall is holding a steep slope surcharge. Having said that though, it is always good to have drainage even on low walls.

You did not specify how they used the gravel. If they have installed it 12" wide and full height behind the wall, then you have a drainage plane. Note in general a gravel trench within soil acts as a gutter - if you insert a pipe into the gravel it will just offer a bigger void to direct water more quickly.

The drainage plane (and pipe within) behind the wall is not a design consideration for limiting water your yard is getting in front of the wall. It is strictly to alleviate hydrostatic pressure pushing the wall out. As a bonus it will limit waterfalling through drystack retaining blocks that will stain the faces. If you have a steep hill and your swampy yard is because of the sheetflow down the hill, that should be addressed with swales above the wall.

Thanks everyone for your thoughts on this, I really appreciate it! I spoke with our landscaper this afternoon and he said he can definitely put a drainage pipe in even though he doesn’t think we need it. I said it will make me happy knowing it’s in so problem solved :)