I've actually found that most science is whatever the particular book's authour felt like saying. Usually they won't say anything wrong but it's not at all unusual for some authours to present one part more fuly while downplaying or managing to avoid some other part either from a biased sense of belief or in some attempt to water down a subject to make it more understandable to the masses. For example someone taking pilot's training doesn't need to know all the ins and outs of Prandtl's lifting line theory to be able to fly. So the books often give the generally watered down Bernoulli explanation or perhaps mention a little about Newtonian downwash. It depends on which book you're reading.

From actually flying I can say that the amount of adverse yaw is related to the aspect ratio. Longer gives the AY effects more leverage to work with. It is also related to the flying speed. Or more accurately how far up the lift vs drag coefficient curve the wing is operating at. At the higher lift coefficients adding camber and angle of attack with a down aileron movement will add a lot of drag for a small angle change at this point in the operating range. Meanwhile if you look at the typical chart shapes reducing camber and angle of attack on the up aileron side doesn't make as big a change in the drag. So the response at slower speeds is to generate a lot more AY than at higher cruise speeds where an angular and camber change makes less of a difference in drag.

I had a buddy locally that wanted to fly an electric scale SPAD XIII at "scale" (in other words super slow) speeds for his model. In his efforts to avoid AY he used a control linkage that generated only up travel in the ailerons. Yet he still had AY and required some rudder to get a smooth turn entry. I finally convinced him to just try flying a little faster. He found that the AY went away with about a 5 mph increase in flying speed. The only effect was to bring the lift coefficent down to where the wing with no aileron travel and the one with the up traveling aileron were both generating about the same drag by being down more into the vertical region of the lift drag curve.