I think you'll find that - - -
1. The prestige was the lightest derailleur system ('cept for huret jubilee)
2. MAFAC made the lightest centerpulls
3. Stronglight made the lightest cranks (name not a misnomer)
4. AVA rims were pretty darned light (like 300 or 330 grams)
5. You can do a lot of lightening with tires
6. I have 531 forks in my garage that vary by 120 grams. Crown and gauge.
7. I weighed several 531 frames and they varied by up to 100 grams in
the same size. It all depends upon lugs, BB cutouts, tubing gauge,
etc. http://www.ece.ubc.ca/
So 21.5 lbs is quite believable for some sort of mid-sied (54cm? 56cm?) Peugeot, if they were careful although I find it surprising that they used ATOM 700 pedals (with steel cages) on these bikes ..
My 77 Carlton Pro is 21 lbs in 24" size, with no titanium (***), although I cheated with MAVIC 501 hubs, and UN-72 BB, and alloy headset.
http://www.ece.ubc.ca/
- Don Gillies San Diego, CA
(***) after adding back 0.3 lbs to convert the saddle to steel rails.