Eric you made a great point.
Through my years trying cues and playing pool, I have been through the same road as many members here on AzB.
The first cue, making balls with it, stringing balls together, getting better, knowing more cues, changing cues and getting used to new cues, then changing cues again....
At first my focus was on how to pot balls, that was when deflection was the biggest focus. Then the process of changing cues raise another question, how much deflection??? This is actually the fun part that most cannot quantify. Cues are different, shafts are different, even 2 shafts paired with same butt produce different squirt and deflection. I played with LD shafts for 2-3 years and every time I changed the tip the cue reacted differently. My LD shafts changed over time also, they got weaker.
When I focus on deflection, it took me 6 months to change from LD cue to a custom, which was a sugartree.
since then I have changed multiple custom cues, all solid maple shafts, but my perspective changed. for 3 years now I dont care about deflection, I care about "feel", how I feel the cue ball will go if I put an amount of side spin on the cue ball, and if that spin will throw the object ball into the pocket. That being said, my priority has changed from potting the ball to learning how the balls react, and more on cue ball action than object ball, because the object ball will need to go to the pocket. but how much power, how much side spin, etc will decide different reaction of the cue ball.
That is when I build up my game differently, when I change cues I just practice random pottings and see how cue ball reacts with my stroke, tip, power; that helps build up "feel", which helps me get used to new cues much quicker. days instead of months like when I looked at deflection first.
My point is, deflection should not be that much of an issue when you play pool, in some situation, deflection is actually a good weapon to use. every cue, even every shaft has different deflection, and even different ppl may produce and see deflection differently, and if you cant quantify it, feel is a better thing to study.