I doubt your contractor installed “mortar” 1” deep on the ground. They probably used a fine mix of sand and pebbles.
If the wall doesn’t extend below the frost line, then a dry set rock wall is probably best.
Any mortar between the rocks/stones will crack because of movement. Movement can be from settlement (because of inadequate base) or frost. When you see cracked mortar, it looks like the wall is failing. That’s why a “glued” wall (as you call it) is better than mortar.
It’s better to install a dry stacked wall like this:
I like a few cavities on the face where plants can grow, bloom, etc. and soften the rock face. However, I’d install a filter fabric or gravel curtain behind the wall to slow the movement of soil through the wall.
Note: A 24” high wall is not high enough to apply a significant enough load to cause it to tip (fail). In addition, the wall has sufficient holes and cracks to allow water to deep out and relieve any horizontal pressure.