User blog comment:David Bear/Sonic's home world is in fact Mobius, not Earth/@comment-477304-20130419215734/@comment-477304-20130419221143

The description seems to be taken from the manual, but the manual doesn't mention Mobius. I assume this description was made by someone from Nintendo, and I don't think that would be reliable enough. Especially considering there has been more than one port of STT made by Sega, which do not mention Mobius.

In short, Mobius is a concept from the Early Sonic Canon and is largly demist in the current continuity.