I moved all my radiators away from under windows (and upgraded the windows to triple glazing) to avoid maximising the temperature differential and energy loss through the wall under the windows, while eliminating the cool drafts that the under-window radiator placement was intended to counter.
My house (built in 1916) was insanely over-provisioned. When we upgraded to a modulating-condensing boiler, we halved the BTUs and are still able to easily keep the house heated to any desired temperature even on the coldest winter days.
The windows all still open, but in winter we have (nearly) enough MHRV (Mechanical Heat Recovery Ventilation) not to need to ventilate directly, eg see:
I'm not sure, but I think that the reason that radiators are placed near windows (at least historically) was to avoid hot/cold spots in rooms.
By placing the radiator near the place that is likely the coldest place in the room, you ensure that the room is an even in temperature as possible. Rather than to counteract 'cool draughts'. I think.
So perhaps people thought that your initial comment was wrong/misleading.
But if you have triple glazing and this mitigates the heat loss, then the coldest wall of your room may no longer be the one with a window, so you may well be doing the right thing for your room(s).
Even if the coldest wall is still the exterior one (it should be, thermodynamically), best maintaining comfort in the room need no longer be by pumping heat out through that wall (or window) to reduce thermal gradients in the rest of the room. Those residual gradients (and, eg, cold drafts down those cooler exterior walls) can be small enough to not need fixing any more.
