What Keystoker calls a "bypass loop" is really an "equalizer loop"...but it sort of functions as a bypass if you have it piped correctly.
The way that Wiz has his piped, some water will flow through the "bypass" due to a pressure differential created by the circulator, but how much is a mystery and uncontrollable without a valve.
EFM recommends installing a valve in the return between the boiler and the bypass, this allows you to throttle how much flow bypasses the boiler. This is useful when you have a high mass system such as a converted gravity hot water system...the hundreds of gallons of water take a long time to heat up, and adjusting the bypass reduces the volume of cold water that hits the boiler.
The other reason to install a loop from the supply to return, with or without balancing valves, is to keep the temperature in the boiler uniform when it is idling. Van Wert called this a "bypass equalizer ". Without it the water in the boiler will stratify and the hottest water collects at the top of the boiler. Notice in the illustration that the equalizer loop connects to a separate port in the boiler, it is not connected to the return piping.
In this case I would add a tee in the piping coming out of the top of the K8 and connect it to the unused return port. This will prevent water from stratifying in the boiler. Considering the large mass of the boiler compared to the small diameter piping and water to air heat exchanger, the system should operate fine without a true "bypass".