I believe he means a tube between the spectrom machine and your extruder weather or not the extruder has a tube after it. You'll notice that both the machines the Spectrom was tested on use direct extruders rather than Bowden tubes.

If you do have a significant distance between the extruder and the hot end (such as a Bowden tube), then the machine has to account for that extra length, I assume with some calibration process..