Well, there’s a sound reason why this happens, in the story: it’s a way to cut to the next scene. John goes to Baker Street and we will see him walk by this wallpaper,
It does, however, like other editing techniques in TST, make it look like this is Sherlock’s dream or imagination, doesn’t it?
The idea that Sherlock has been at Baker Street, ‘this whole time’, is certainly been strong since TAB,