This device will operate very differently depending on flow rate, therefore the quote "the device acts as a slightly leaking valve" is probably a bit misleading

This device will operate very differently depending on flow rate, therefore the quote "the device acts as a slightly leaking valve" is probably a bit misleading. The Reynolds number determines if the fluid operates in a turbulent or laminar way. The slower the fluid, the lower the Reynolds number and the more laminar it becomes and thus the less effective the valve is. I can't really see many uses beyond microfluidic applications.