Did Spainkiller ever hear back from his source? I'm leaning towards their source (somewhat) honest due to Mewtwo and the connectivity stuff (didn't someone else vouch for them too?), but the whole Ridley aspect could have just been a scrapped level boss for Brinstar or a Pyrosphere port like Yellow Devil being in both versions. I get that Other M Ridley's just a clone of the *real* Ridley, but it'd a bit too weird at this point to pull the rug from under everybody if that's what they were planning.
Apparently the Ridley model on the 3DS was the Other M design as well. I'm leaning towards it being a boss for a scrapped Pyrosphere port in that version - it makes sense that due to Ridley's higher complexity compared to Yellow Devil, he may have caused issues on the weaker 3DS hardware - probably why Metal Face doesn't show up either. And unlike Xenoblade, Metroid had a past stage to fall back on, allowing Pyrosphere to be abandoned entirely.
Though I wonder why they didn't use that model (along with the scrapped 3D Flying Man) for a trophy...