It looks like the rebate only applies to reservations made on the Japanese JAL website.
I see this in the exclusion list:
JAL海外サイト（海外発航空券
Translates as: JAL foreign websites (tickets issued outside of Japan
Nevertheless, I tried following the 10% rebate link, and got to a JAL page that only allows departure from Japan. From this page, I could navigate myself to a more flexible reservation page but probably the rebate doesn't apply there.