Um, no, actually. It doesn't create the discard pile until after all is said and done, which is why it didn't show Mirror golem. At the point in which the game created the list of discarded cards, it looked at the slot that contained the Uncommon at the start of the turn and saw that the Rare had replaced it. This is a known issue that has been discussed in the past and confirmed by Mojko.
I understand your preference for Mojko's word over mine, but it is an issue he's addressed himself already, so it is what it is. I'm sorry if I've come off as obnoxious in any way, though I won't apologize for being a pedant. Most programmers are out of necessity.