First of all, sorry for pull old post, but is same topic , so I think no need re-open new one.
Since this post open day, until EoD release after one month, this problem and related thing still not solve for long time.
also based on this period , I already see many missing achievement data cant fetch from this API. (which should whitelisted or appear for public.)
I hope developer fix it.
also hope can leave/add back those old but exists in /account/achievements that can match and found in /achievements API for info.