A few points:
1. Typically sports photographers are using longer lenses which depending on the apeture used, tend to compress objects in the final picture ie. they appear closer together than they really are.
2. Pictures are static - there may have been a fair amount of fore/aft movement of the cyclists relative to each other, in each of the pictures that can't be picked up in a snap-shot. And that's what officials are looking for - movement relative to other cyclists.
3. I have heard it said that in Europe they are a little soft on the drafting calls compared to big races in North America.
4. There are times and places in big competitive races when the no-drafting rules are asking the athletes to do something that almost impossible to achieve. There are simply too many cyclists on too little a stretch of road. You see this in almost all the big Ironman races about the 1:00 to 1:10 mark. It's for the most part inadvertant drafting and again I have heard that officials often turn a blind eye to this.
Steve Fleck @stevefleck | Blog