Interesting.....
All I can say is the watch is not a laser pointer and is not designed to measure paragliding. If you have good technique and skill then my testing and others comments show it gives meaningful results. I can guarantee that mid jump lofts, or 1 minute long hangtimes will not calculate correctly on my app, and I would speculate on any device. It's not an aircraft barometer.
If you're using the Beta, I have no comment as there have been updates since then, but my above statement regarding mid jump wind phenomenom, such as micro bursts, dust devils, updrafts, boat towing, jumping off objects would apply in all scanario's.
Better off paying the $60 a year to see if that works :) or spending more on one of the other devices to see what they say, I would be very surprised if you got something meaningful.
My session of 30 jumps was pretty much there. All registered and heights in the ballpark.
If you want more accuracy - put your watch somewhere else ( shoulder in phone holder, or attach it to the harness somewhere ), you will get the highest accuracy possible.