SM, I fully understand your reasoning and in normal situations its true. I know that I'm perhaps the only windsurfer with such a leash

But, be assured that I have my reasons. They have to do with some complicated physical defects of me and with the xtreme circumstances in which I sometimes surf.

The leash I use already more then 20 years after an adventure in wintertime when I lost my board plus sail crossing from the Mainland to Texel. There were gusts so heavy that my wishbone was ripped of my hook and my hands. By some exceptionally chance the sail and the board created together some horizontally kind of wing and I saw it flying away from me above the water. Far away from me.
The current overthere is one of the strongest of Holland, so it seemed impossible to catch up my gear by swimming.

I was almost forgotten this the last decade but that was also one of these close escapes, only it was not under water.
And also then I experienced this impossible power you can have when things are really bad.

So, I will not dispose of my leash, I wear a full life jacket already for 25 years (after I lost conscious in a hit against my board during washing) and I ofcourse I have a safety around my mastjoint.

Sailing in general is always pondering about pro's and contra's of certain dangers and the precautions you have to take.