This is the ideal, but it's often false in meaningful ways. In several US elections, for example, we've seen audio leaked of politicians promising policies to their donors that would be embarrassing if widely publicly known by the electorate.
This suggests that politicians and donors sometimes collude to deliberately misrepresent their views to the public in order to secure election.
worse.. a first-hand quote from inside a California Senate committee hearing chamber.. "Don't speak it if you can nod, and don't nod if you can wink" .. translated, that means that in a contentious situation with others in the room, if allies can signal without speaking the words out loud, that is better.. and if the signal can be hidden, better still.
This is an old saying in politics and you're misinterpreting it - it's not about signaling to allies, it's about avoiding being held to any particular positions.
You're also missing the first half, "don't write if you can speak, don't speak if you can nod, and don't nod if you can wink." The point is not to commit to anything if you don't have to.
This suggests that politicians and donors sometimes collude to deliberately misrepresent their views to the public in order to secure election.