My two boys were like that in the beginning too. What seemed to help was two of the same dog beds next to each other. Each has his own "space," not necessarily defined, they both sleep in whichever bed interchangeably, but it makes them feel like they have their own space. My dog beds also have a raised pillow section so it feels a little more separate.
I'll save you guys the read on this one. It's absolutely 100% based on nonsense. There are no peer reviewed sources for this and all the "references" are anecdotal and from Twitter or other social media. There was no study, no research, and no scientific basis whatsoever for this "article."