Well I do have a thought... If the shatterverse, as it is known, was wiped from existence how does Sonic and Shadow remember it still? Also the shatterverse still exists, just that Sonic can't survive in it seeing as he would need Prism energy in order to return there. I did notice that the ending is set back to the events before Sonic shattered the Prism. I wouldn't say the shatterverse no longer exists though it just exists in a different reality post-shatter and pre-shatter. I hope what I said makes any sense...

8:38 you could also maybe count this as a reference to Metropolis zone and Grand Metropolis from Sonic 2 Heroes and Forces