I recently attempted to redeem HND-KMQ on JL using QR avios via the web form. The avios cost is 6,000 on QR vs 10,500+£0.00 through BAEC, but after the reservation was made by QR, I was asked to pay 7800 JPY "for taxes". The cash full cash ticket price is only 11000 JPY and there is no tax or fees on Japan domestic flights.
I also attempted to buy via Iberia even with their no changes limitation, but I get an error message when trying to book any JL flight through Iberia.
This was my first attempt to book an award ticket with Qatar Avios and the juice is just not worth the squeeze.