I'll agree that keeping specific achievements out of that mode was probably the right move. Those that like achievement hunting dont want to be put off by ones that are SO difficult as to be almost unreasonable without an incredible amount of practice and such. I've seen the occasional game do that one, and it usually just leads to complaints. Lots of them.
And this particular difficulty is, well.... I'll just say, I'm sorry.
As it is I think many players will find plenty of challenge in getting the Expert ones, so that should work out pretty well.