I'm a bit out of the loop here, can you give me a summarized version of the two worlds setting concept? Because maybe I don't understand what the original intention was, but I could've sworn that there was always ever going to be one world inhabited by the furry characters and humans
It's confusing, so I'll try to state all the info I remember. Back then in early Japanese Sonic lore there were two worlds, one is the human world and the other is the fairytale world, the fairytale world had its story told by a woman as storybooks. This was like, used in a few guidebooks and manga and although never addressed in the games themselves, that was accepted from the Japanese-side and IIRC one of the reasons the Sonic movie never happened back then was because Sonic Team requested that to be the official Sonic lore (In contrast, Ken Penders wanted to make an Archie-related movie so that his lore would take over the official lore due to becoming more well known).
Years later this lore was basically never used again, but people like Yuji Naka and Naoto Oshima both would answer in Q&A about the lore and there was a clear difference. For one, the Sonic world existed in another world different from the human world, it's just they overlapped a few times. For the other, Sonic existed in the same world as humans, but in hidden regions that were affected by nuclear tests and other stuff that mutated them into what they are today. I can't remember well who said what, but I think Naka was the one going for the same world and Oshima was the one going for different worlds.
Years later when Takashi Iizuka took over as leader of Sonic Team, sometimes he would answer fan questions and sometimes, he used the lore about the two being different worlds, but it was never addressed in the main material itself, so the only explanation about this stuff were in two places. One was Sonic Forces, as the designer explained he used the Two Worlds lore as the reason why he made an entire language for the animals as he understood they were like aliens from another world, so they had their own language. The other was Ian's bumblekast in which he would often comment the notes he got about the two worlds (Like explaining that hidden in caves there were huge golden rings that were like warp portals between the two planets. He also thought they were like worlds from different dimensions, but when he asked again he discovered they were just two planets in the same universe, but far apart). Still, Ian hated that lore just as much as many other fans due to being so unusual and nearly nothing in the games really stating that.
The truth is that the Two Worlds only existed as background detail and supposedly was the reason for why there a lot of strange stuff between a few games, the explanation was that there were more than a single world (So sometimes in the background of Sonic games there were more than a single moon). But that only existed in records, in fact the only reason why it first started to be talked about was in old Sega Forums when a mod started to discuss about the Japanese Sonic Bible and all the stuff from it, disliking what was there.
Eventually when the plan to unify the Sonic lore started, the whole idea of Two Worlds was ignored in favor of the current TailsTube explanation. It might have been fun for Ian to write about removing something he hated from canon.
