I just got the achievement through Dragonflight Keystone Master: Season Two, but didn’t receive the item Draconic Mark of Mastery. Have tried relogging, didn’t help.
I’m about 99% sure this is just an 1 time phenomena of the timer adjustments to UR, FH, and Uldaman that went live recently, and M+ scores not being re-calculated until the person finishes a key.
It should be safe to earn the achievement now and collect your reward. Anyone who’s earned the achievement prior to this fix will earn their reward early next week.
This is a bit of a kick in the teeth to people who earned the achievement while it was bugged, if we aren’t going to get the token until after the reset, especially since a lot of people sought out this token specifically for progression raiding