That you are not supposed to lie to lawyers and doctors is a known fact. I add marketing agencies to it for what I believe is a good reason.
The urge to perform better (read please the VCs) and at times perform better than your own in-house teams, makes you start a relation (with your marketing agency) with a lie. Hunger for sales incentive (comon let’s be honest at least with this) makes them accept it even as they know you are bulshitting them and vice versa.
Do away with it. If you can’t be transparent with them, don’t talk to them. You won’t be any better off than where you started.
Side Note: Shouldn’t lawyers, doctors (and agencies) be equally honest and truthful?