Flew back on Saturday morning on the AM 767 flight which was going out of D53 instead of the other pier. I don't know what the other pier's gates are like, but after going thorugh security, you were in a "pre boarding pass" section. They started "preboarding" and I with Sapphire and Euro Traveler were allowed to pass (they made some generic call for Club Europe and I just walked up despite my class). We all then were "moved" into the next section, but were not allowed to board yet.
By the time boarding started, you pretty much boarded in a free for all depending on where you were standing, but it sounded like the agent near the door was "asking" whether you were in Club...I passed and boarded so not sure what happened after that.