Let's consider this in a positive light!
My Omni VII was very quiet and I doubt there ever was, or is, any issue with noise because it had a plastic front panel. As the tooling for the original panel is unavailable, TT fashioned new one from aluminum and it stands to reason, based more on logic and common experience than on technical proof, that an aluminum panel will better shield rig from external electromagnetic fields than a plastic panel.
I highly doubt TT did any serious testing to prove it, and I doubt it solves any sort of "problem." I accept the claim solely on logic and common sense. Shoot, I imagine they are simply putting a positive spin on having to re-make the front panel, and that works for me.
Come on .... a metal panel surely provides better shielding - right? And surely aluminum is stronger and more durable than plastic, right? It does not solve any sort of issue - TT is simply making lemonade from lemons, and looking for the silver lining, as it were.
I say we just go with it ! As my favorite Drill Sergeant used to say, "Drive on soldier!"
Just MY take. K8JHR