@naamang, the listed features of the WFM don’t imply controlling flow rates. “Monitor flow rates” and “fine-tune watering accuracy” don’t imply automated adjustments for varying pressure, though that would be nifty and seemingly possible in software. But consider that if pressure induced varying flow rates were accounted for, then leak detection wouldn’t be possible, absent pressure data fed to the unit. One or the other it seems to me.
Also, heads perform wildly different at varying pressure. From distance thrown to misting, which would throw off the theoretical gain from doing a simple gpm/ft^2 calc. I’d stick a pressure regulator on the line into the irrigation system to get consistent head performance first and foremost, which would seemingly eliminate your problem of irregular flow rates. I went with individual pressure regulated bodies with my heads for that reason, and pressure compensated drippers on my drip zone. Given the fully pressure regulated system I now have, the flow meter gives solidly consistent flow rates. My city incoming varies from 110 to 70 psi over the course of the year and it doesn’t matter.
Obviously the meter and setup don’t fit your needs, no argument there. I just don’t think your assessment of dishonesty is accurate.