"highest achieved rank last season"- bug

So when i logged in today, i saw that my "highest achieved rank" was stated as platinum 3. But that is not true. My highest achieved rank was platinum 2 during this season, and i dropped in plat 3, 2 weeks before end of season. Because i didn't expect to get higher then plat 2 anyway before end of season i didn't bother climbing back to plat 2. In past seasons you got your highest achieved, not last achieved rank.

I hope this is a bug and not a decision made by the devs. You can see my rankings on League of graphs .com