I have contracted a garden firm to build a concrete block wall and curved steps. I don't think they know what they are doing as the blocks are sitting on the dirt and are very narrow. How should they go about this?

I have contracted a garden firm to build a concrete block wall and curved steps. I don't think they know what they are doing as the blocks are sitting on the dirt and are very narrow. How should they go about this?

Please see the following links:

Concrete Block Retaining Wall

It looks like they should be on sand.