Yea, i have not gotten any of those. I only had one alrune part
Oh almost forgot they also only appear when losing because of corruption if I remember correctly. But since you haven't seen those you didn't get the Alraune Bad end which woud have triggered the achievment so it might be a bug.
I will try to replicate it when i have time and get to the bottom of this.
Thanks a lot for the reports!