One place where the up elevator coupling from a swept hinge line would show up would be during a wingover where a lot of rudder is being used. If it were a strong effect it would try to loop the the model over onto it's back at the same time it is producing the yaw needed for the wing over.
As you say though often we don't use a whole lot of rudder angle. And it seems to me that if one did a top down view of the "elevator" exposure area of the rudder as it is deflected there would only be a decent amount of area when at larger angles of deflection. At moderate angles not so much. So it's not like the up elevator effect from the rudder's hinge angle is directly related to the angle itself equally across the range of movement. I'm sure there's a mathematical way to describe this but for me it's easier to do it in CAD...So 10° only "sees" an elevator exposure of 6% area while 30° "sees" more like 16% of the rudder area. So it's a sliding scale based on the angle of deflection. And really other than model gliders not many models use much over 15 to 20° of rudder deflection.
To me this pretty much explains why I have not seen a noticeable effect from a swept rudder hinge line in my model flying. It's certainly there, but it's such a small effect for reasonable hinge line angles that it's overshadowed by other factors at any sort of normal hinge line angle.
I also suspect that because of the way the air flows around the rudder that there's some reluctance to deflect upwards when it's easier to slide sideways around the rudder. So my guess is that while the angle will lift the air slightly that it won't match the percentages. Especially at the lower deflection angles.
If we laid the hinge line down at more like a 45 or greater angle and fly rudder elevator style models which require more rudder deflection then I could see the pitching couple becoming significant and noticeable in flight. But it only shifts the point of needing to apply elevator in a turn to that portion where a higher angle of rudder is needed. Once into the turn and holding just a sniff of rudder angle to maintain the turn size we'd still need to use the usual amount of elevator.
Thoughts?