Experiences with Non-Isolated Void Systems for Under-Slab Plumbing?

Has anyone here used non-isolated void systems for under-slab plumbing, especially in areas with expansive or shifting soils? I’m trying to understand how these compare in real projects to isolated approaches like the Mudskipper system that suspend and isolate plumbing from soil movement.

With non-isolated void systems, the plumbing sits in a void below the slab but isn’t fully isolated from the soil — the idea is that the void space provides room for soil movement without stressing the plumbing. On paper it sounds simpler and less expensive than a fully isolated framing system, but I’m curious about how it behaves in practice once the soil starts heaving or shrinking over time.

For those who’ve installed them:

How did the system perform long term?

Did you see any issues with plumbing stress or joint failures?

Was the installation noticeably faster or cheaper than isolated methods?

Any tips for detailing or choosing between isolated vs non-isolated void approaches on projects with expansive soils?

Would love to hear real-world feedback from contractors or designers who’ve worked with these systems.