I like the idea that the Drust possibly play a role in whatever vision of the "Rootlands" devs had (regardless if we go there or not).
I'm not totally sure the Trading Post items are recycled from cut content, but I agree there's no way they're from Shadowlands. I think the Drust are a cool enough aesthetic to find excuses to bring them back in content like the Trading Post. Almost like a precursor to the Arathi in the sense that it was new lore that was overwhelmingly accepted as awesome (I think?)