Rupp's 5k AR is pretty impressive.
However, last week I was doing a 5k tempo on the indoor track at my school. Keep in mind I've only been doing base, and I did the 5k SOLO. Anyway, I clocked an 18:21 (if I counted the laps right). I think had there been competition, and had the track I was running on been banked I would have bettered Rupp by at least 18 or even 23 seconds.
So, although what Rupp did was impressive, lets not get too hung up on an AR being broken that stood for 27 (?) years!