Twelve years ago, the term hydraulic separation was very new to the vocabulary used in the North American hydronics market.
Back then, the contemporary topic being discussed and applied was primary/secondary piping. The idea that several loads, each served by their own secondary circuit and associated circulator, could be connected to a common primary loop with its own circulator. The “magic” of closely spaced tees is what prevented the flow rate in any of these circuits from interfering with the flow rate in the others.