emphasis on "facing a good, orgnaized team". If the other team is weak, not interested in the objective then all best are off however a quick "I am pushing A (or C)" would be at the very least polite.
I closed out the Dom challenges long ago but am always happy to help somebody else get the Trip Cap; just prefer a heads up. And not when we are going against a decent group as I would rather get the win- which is often tough enough when you get into 300-400 SPM opponents. You end up trading B the entire round.