I understand the link, however, Leiby a’h didn’t die al kiddush Hash-em. He was murdered without anyone knowing at the time. The result of his untimely death is a tremendous amount of davening, learning, and chesed. His death brought about a kiddush Hash-em. That is his zchus. Maybe it’s just a technicality with the difference of time.
In terms of it being a gilgul neshama, who knows. It’s speculation at best, but if a person in their lifetime wants to have the zchus of dying al kiddush Hashem, shouldn’t they have that zchus in their current lifetime when they mean it, versus another, when they wouldn’t? Again, an emunah and bitachon issue.