They aren't going sideways. The show is switching between alternate universes or timelines. So we should call each change in perspective a worldflash or timeline jump or wormhole jump. This lame idea to call them 'flash sideways' is awful, like it was written by a 10 year old just learning to put together words in English: it's an uncreative, infelicitous phrase.
If you don't like my suggestions, what do you suggest (besides the totally lame 'flash sideways')?