It’s hard to tell from the picture. Stick a ruler down in the mulch so that it’s touching the actual dirt and then report back with how many inches deep the mulch actually is.

If only 3-4 inches thick, it is fine. It will compress or collapse slightly with time. Just avoid burying the crown of any perennials/grasses and maintain a distance away from the trunk or stems of any woody plants

Thanks! All the crowns of the grasses are under the mulch. Some of leaves (and branches of the plants) were buried as well. I just measured the bed. The areas immediately around the plant is 3" (meaning the plant is buried up to 3" in mulch), while other areas of the garden have up to 7" of mulch. Should I ask them to move the mulch away from the crown?

Your photos do not show any crowns being buried. Mulching right up to the base of herbaceous plants is fine but any parts should not be buried. And 7 inches elsewhere is overkill! A layer that thick can prevent water penetration down to the root zone and your plants could die from lack of water. Get your landscapers back to even things out to no more than 4" max.

Are you on drip watering?

The final result - wall, mulch, plantings - looks nice.

Good question from socks. Are the emitters are way down in the mulch, right above root zone? If so, then water reaching root zone should not be a problem, I would think, with even thicker mulch. Disclosure: I don’t do this as a profession, and I have never once worked with drip irrigation.

Thanks everyone! We talked to the landscaper and he's going to remove a little bit off the top and try to smooth out other areas that has too much. We do have drip irrigation that's under the mulch so the plants will get moisture. I am still trying to figure out what's the right amount of water for these native plants. Hope we don't kill them too soon :). We are very happy with how the wall turned out. I'll upload final photos of the project tomorrow. Thanks!

If these are new natives than they will need regular water for at least the first year. I guess that I, personally, don't like the mulch so close to herbacious plants. I'm always afraid they'll rot, or get moldy, or something. It's not the way they would grow in nature so I'm always leery about too much mulch so close.

Once I had mulch like this without drip watering, and the mulch just absorbed sprinkler water. But with drip you should be ok. I think it’s too much mulch. When he removes some, save it in a pile somewhere if you have room.

I hope it's not up against that fence. Maybe it's dry enough it won't matter but here in the humid Midwest it would rot the fence.