There is, and MUST be, transference of load from nose to mains.
Consider the simple levers that keep getting quoted herein. Three points of action/reaction. The nosegear, the main gear, and the tail. Mains are equidistant from nose and tail, to keep it simple.
Suppose the aircraft to have, under whatever braking, reverse thrust, whatever condition, to have zero tail load, and 10 tonnes of load on the nose gear, and 90 tonnes on the main gear (total). In equilibrium, in pitch.
Apply X tonnes of down force at the tail. Taking moments about the nose first: downforce must increase at main gear by 2X tonnes (since nose-to-tail is twice nose-to-mains).
Therefore, since we only added X tonnes of down force to the system, but appear to be pushing down more on the ground by 2X at the mains, we must be removing X from the nose also. Calculating the moments about either main gear or tail shows this, as does consideration of the vertical force balance.
Therefore in addition to adding our X tonnes of aerodynamic downforce from the tail to the mains, we are also effectively TRANSFERRING X from nose to mains.
If the ratio of nose-to-main and main-to-tail is not unity, the exact numbers change, but the principle doesn't; the only way a lever can act to INCREASE the download at the main gear relative to the applied tail load is to decrease a force somewhere else.
Now, for any given type you can calculate the ratio between added mainwheel download and nosewheel unload, and make a specific calculation for a specific tail load.
You can then calculate the amount by which the aircraft WILL pitch as a result, as the main and nose oleos re-adjust to account for the change in load.
You can then calculate what change in wing lift will account for the resulting change in AoA and compare that to the direct load increase.
If the transferred tail load effect outweighs the wing lift effect, you have NET increased mainwheel download. If it doesn't, you've actually unloaded the mains.
Whether a given aircraft is particularly nose up or down in tendency doesn't matter to that; all that matters is whether the oleos are fully compressed. Except in exceptional circumstances, they are not. Therefore increased download at the tail must pitch the aircraft.
The factors which will determine the effectiveness or otherwise of this method are the relative nose-main-tail geometry, the stiffnesses of the oleos and the sensitivity of the aerodynamic lift to pitch changes. It's not a one-way bet, and depends on how those interact. As the oleos approach infinite stiffness, the backstick method becomes more viable; as the wing effectiveness improves, the backstick method becomes less useful.