I've just spoken via chat with DJI support about this issue, and the tech said "our developers already addressed that issue, and they advise that you need to refresh the firmware of your drone if you will be using the low noise propellers on your drone." I too have been using LNPs from day one and have never noticed this warning until recently, which appeared in the flight status area of the app as opposed to mid-left screen with "x" to clear option. It was displayed so briefly that I did not catch it during flight the first time and only discovered the first instance by playing back the iPhone screen recording. This warning also does not appear in the flight records viewable on Airdata, though every other warning/notification does appear in the list.