"This rational action did not prevent the DHL Boeing from colliding."
This rational action(following the RA) would have prevented the collision as the report obviously states.
What would have been and what was are two completely different things. Fact is that the Boeing crew did behave just like you said you would. You said, that this would be the rational action. This must mean: following the rational course of action did not prevent the collision for the Boeing crew in the Ueberlingen case. The mid-air itself proves this.
Arguing about what-if is a completely different matter.
Had both aircraft followed the RA, the mid-air would have been prevented.
Had there only been the resolution issued by the Controller, the mid-air would have been prevented.
Had TCAS issued a reversal RA for the Boeing and Tupolev, the mid-air might have been prevented.
Had the STCA been available for the controller at ACC Zurich, the mid-air would have been prevented.
I could go on like this for pages ...