I’ve had my handlepass leash come undone once, a couple months ago, on my Session 1 harness in 2 years of use. It happened during a massive crash (learning to kiteloop, unhooked) but luckily I was leashed to the spreader bar at the time. I don’t know if the release snagged on something or just came loose. I now check to make sure the release pin is well seated before going out and haven’t had any problems, but I have and still am seriously considering disabling the system.
I agree about the pin length - if I need to activate this system I am going to be pulling so hard that an extra 5-10mm of travel before release will not make a difference.