I could be missing something obvious, but I have not been awarded the in-game Diploma achievement or icon despite having the steam achievement awarded to me, and a 93/93 on the campaign stats in the top right. I did also play the last level and watch the last cutscene again, in case that was a trigger to award it, but it did not work. If the criteria for the in game achievement happens to vary from the steam achievement and this isn't a bug, I feel that is a little confusing. I can only attach 1 screenshot it seems (unless I am dumb) so you can see my having the steam achievement