Yes, you are right; nothing new under the sun, contemplated 1984 already as working on oxygen mixers…
Shifting the middle-point on the boom between 2 membranes instead of
keeping track on the difference between arriving gaspressure and regulated airpressure is putting things completely “free-floating”!!!
First we have to have available “arriving” gas and air on the same level, before we are attempting to dispense controllable flows!
Short cuts are no perfection, when doing good work.
There is no controllable dispensing, if one flow-leg is the arriving gas pipe, and the other leg is a pipe with a flap! The dispensing throats have to be identical after pressure difference sampling and established control thereof.
Reality is harsh, sometimes…
When arriving pressures and flows are equal, we can start a controllable dispensing to the best of aims.
Under which cathegory did you find the lego video?