This is a concern that I've heard on several occasions about IM Barcelona.
There seems to be no/little opportunity for strong cyclists to gain time over weaker ones. Instead it's almost like everybody is waiting for the run so that they can start racing again.

I was interested in doing this race next year but, after chatting with a female pro that I know, have been put off. She described pretty much what your picture shows above, and talked about what a nightmare it was to try to avoid drafting. She was saying that whenever she dropped back so that she was out of the draft zone, somebody would overtake her and unapologetically sit within it. because of the general peleton effect, she did a 4:5x bike split. By her own admission she's not that fast, but she was left with very little option but to just go with it.