Oh, what were you doing when it was awarded? maybe it is something awarding the wrong achievement.
I don't remember what I did at that time... I know I was going for doing these achievements:
Quantity Not Quality
Do not upgrade any soldiers and win the level "New Home" on Medium difficulty.
Unlocked 20 Mar @ 10:12am
Speedy Setup
Win the level "New Home" on hard difficulty within 17 minutes.
Unlocked 20 Mar @ 10:12am
Picky Eater
Win the level "New Home" with the last 10 tunneled out creatures being woodlice on Insane difficulty.
Unlocked 20 Mar @ 9:58am
all in one go, restarting when every time because I was too slow. (17:44) Oh... hmmm... The one insane session I did that could have earned me that achievement was started at 09:16 am CET... That can not be the session that awarded me the achievement, because a different session started after it but before 9:58...
I have no clue if it is bugged or not...
Edit:
Just assume things are working as intended, if anyone else has this issue they will very likely see this and report on it.