I tore both wrists badly from too many all day sessions, excessive bar pressure combined with some acute injuries. Soft tissue injuries can heal very slowly. I recommend that you don't use that wrist strap arrangement lest you cause new injuries, TBI, smashed face, etc.. It is all relative. I bought and tried a bunch of stuff including windsurfing wrist "hooks", plastic wrist braces, lifting wrist braces with hooks, etc.. All that crap is just too dangerous when handling a powered kite control bar and should be avoided. The best things I did to improve my wrists included:
1. Back way off on duration and frequency of kite sessions. I would skip a week or more and if I went out limit it to an hour or so. In time you should be able to go out longer. You have to do this to allow some healing to occur.
2. Setup for the least bar pressure possible through kite, board and bar size selection. Go out in optimal wind vs. your setup. I found going out in stronger wind required less holding the bar in with associated wrist irritation.
3. Wear wrist braces such as https://www.amazon.com/BraceUP%C2%AE-Wr ... 66&sr=1-11
4. Find a good doctor to evaluate, adjust and help heal your wrists through PT.
5. Avoid messing up the area through excess or improper lifting, carpal issues through computer use if you can manage it.
Other things included: Ice water immersion of your wrists about three times a day for no more than ten minutes to help reduce inflammation. If you have time, most don't, you could alternate with hot water bathes.
Resign yourself to backing off for a while and if you work at it you be back in time. Good luck!