Yes, used to do it annually before JQ Japan commenced. Always was only Y1,000 at checkin counter - not online and attracted J SC's.
At Asahikawa, we were first in line for the remaining two ClassJ seats. So, it's a bit of a gamble with the AirPass.
I wasn't aware you could book ClassJ online with an Advance Purchase Fare - might have to try that. JAL MB members probably grab most ClassJ online before departure day.
No. Still cant book class J online. Just was wondering if SC treatment is the same for online booking and uograde at airport