IMO, not all outlets are the same. The power supply can work fine in one building and be noisy in another. It can also work fine on certain circuits in the house but have noise on others.I don’t believe the OEM PSU is actually the issue. I have two different OEM PSUs, a OneSpot, and an Omelink, and all of them exhibit the same grounding noise issue. Comparatively, powering Anagram with a Cioks, Sol, Hi5 Mod, or 4 Expander all yield totally silent results. While the OEM is an issue, it appears that all PSUs, at least for me, are an issue if they’re the wall wart variety.
Hard to pin this on the mfg, imo. Some places need better isolation than others. My old house was 100yrs old and a royal pain. My current house is only 50yrs old and much better but I still dont like some of the circuits. The living room is dead silent so that’s where I prefer and the garage the noisiest so I avoid . lol.