So what you're saying is we made a problem for ourselves, and then we hacked on additional cost (and plastic) to fix it?

I'm starting to see the advantages of this dry stone wall technique.

A 'sealed' retaining wall where the stones are interlocked or even glued/mortared together would probably have a higher load capacity than one made dry/unadhered. Or someone could simply like the aesthetic of a more 'filled in' wall, regardless of practical considerations.

Eh, the perforated pipe technique can efficiently collect the water and move it somewhere else entirely. It's nice that dry stone can just let water fall through, but then it just runs out at the base. Which might be fine, but you might still want a french drain anyway.