Oh I understand that, but I was talking about the final selection. What I was describing applies to the situation in stage 9 as well as generelly to every final selection of every race. If you needlessly let the strongest rider in the race or pretty much any professional rider just sit on, you will always get beaten. It isn't about team tactics, it's about basic racing intelligence.
The thing is that podium places, or top 10 places in general, have a value. It's not 100% about the win.
In this case, PFP's lead over the next few places was more than that between those places, so if (eg) Vollering attacks, Gigante, NFB, and to some extent Kastelijn, Kerboual & Wlodarczyk get uneasy about their position and are likely to start to chase.
In addition, a half-hearted attack won't do anything, and a full on attack that's brought back is likely to result in losing places.