Yeah, my post wasn't about whether they should or shouldn't add the achievements, it was just a note that achievements weren't a BC thing.
I personally wouldn't care if they added the achieves or not. So many years have gone by, that it doesn't mean much at this point.
"Oh, you killed heroic 25 man LK before nerfs? Cool, can you play your currently class well now that it no longer resembles anything from back then and can you make raid times?"
Those achieves don't show if a player can play well currently, and 99% of people won't care anyway. Now, I could see why for that 1% it would be nice to have it and I doubt it would be difficult to implement.
/shrug.