On one of my flights today, I noticed after I uploaded it to Airdata UAV that there is a Mode change to 19. The only thing I did in that flight was change to Cinematic Mode during the flight.
Has DJI decided to number the different Flight Modes and instead of describing the mode, they use a number instead?

I believe what's happening here is that the mode is always stored as a number and that AirData just hasn't been programmed / updated to recognize that particular value (19). It'll display a human-friendly name for those it recognizes (e.g., "P-GPS") but for those it doesn't it just displays the number ("Mode_19") instead.

DroneFlying Posted at 2017-4-26 02:14
I believe what's happening here is that the mode is always stored as a number and that AirData just hasn't been programmed / updated to recognize that particular value (19). It'll display a human-friendly name for those it recognizes (e.g., "P-GPS") but for those it doesn't it just displays the number ("Mode_19") instead.

Yes, you are basically right. I had a look back through some earlier flights and notice that Tripos mode is listed, ActiveTrack also appears alternating with Joystick mode. Everything else seems to be Mode 19.