>>30481479The only reason this whole reply chain started is because people are taking Serebii's map as gospel, for some reason.
Like
>>30481654 said, it's much more likely Sinnoh is just supposed to be far north like its real life equivalent. Barring some weird shit like a desert in the middle of Manhattan, most Pokemon regions can more or less be related to the climates and geography of their real life equivalents. Altered somewhat for videogame scales and pacing, but still.
Considering the globe in your room in SM shows a pretty earth like planet, there's really no reason to assume regions are in different geographical locations than their real life counterparts until GameFreak actually makes that explicitly shown.