Why can't I use my Shower Filter with a "low-flow" or "stop-flow" shower head?

Edited

In order to get the correct pressure for proper filtration, the Shower Filter needs to flow at 1.6 gallons per minute (6 liters per minute). This means that shower heads that purposely restrict water flow will most likely result in subpar water pressure, and as a result are incompatible with the Shower Filter.