Plan early, book early, and you will be ok.
JAL is of course trying to lose the stigma of "no award space available when you need to use miles" by doing dynamic award pricing.
Just look at those dates with "horrendous mileage price" as dates that are technically not available with miles, but JAL is giving you an opportunity to still use miles if you MUST use miles to travel. It is an allure.
So, plan early, book early, when the mileage is still low/reasonable, and you will be ok.