On Tuesday, 09/14/2010 at approximately 1:30 pm PST, just a few hours after launch, Halo: Reach’s online unique user count had already completely eclipsed Halo 3’s total tally for the entirety of the week (09/13 through 09/20)
I think you misread the above statement.....what they are saying is Halo Reach had more online unique users in 1 day then Halo 3 had the previous 45 days prior to Reach's launch.
I'm don't think that Reach is actually that badly undertracked (I wish it was though)
I guess time will tell though!