I agree with most answers stating that you can't make a decision for another road user, however, I want to share something that happens on my country, Honduras, were we have a generally poor vehicular culture, and just the first attempts are being made towards motorist accepting bicyclists as legitimate road and street users.
In our roads, truck drivers (18 wheelers) use to swerve temporarily towards the right while flashing the left turn indicator which is interpreted by small vehicle drivers as an invitation to overtake, indicating that the driver of the truck is aware that it is slowing down the rest of the traffic and that those drivers "are there" trying to overtake. The decision, of course is always for the small car driver to make, the truck driver won't get angry if you don't overtake right away.
I have had similar interactions on the road while I'm on the bike and an 18 wheeler driver performed the same signals and even waved with his hand.
What I'm trying to show is that waving for a driver that is behind you is not you taking the decision for them, instead it means that you are aware of their need to overtake and are briefly "willing to collaborate", i.e. you indicate that you won't be taken by surprise is the manoeuvre is performed normally in that moment.
I have also had a type of interaction where I was riding a bike and asked a driver not to overtake by waving my hand palm side down. This was because there where parked cars at both sides of a narrow street. As soon as there were more space, I waved him/her back as I swerved right. The driver seemed happy with the action, and greeted with a couple of beeps as passing by.
I realize this is subjective/anecdotal, but I wanted to point out that there is another interpretation for this type of signals, but also, that this depends a lot on local culture.