a 20 inch power stroke can have ok cast, but as the power stroke gets longer, you usually can get better cast,,24 or 25 seems to be a happy medium for me,, when I test through the chrono,, there can be an increase in cast as I get out to 24 inches, I have had bows that draw 20 inchses shoot 150 fps with 10 gpp,, but as you know a longer draw can achieve 170 180 fps,, faster with really well designed bows,, thats just my experience with mostly straight tip bows,, but I have shot alot of 20 inch bows through a chrono ,, just to see what they can do,,,at close range 150fps with work great for deer,, if you were shooting a 60 or 70# bow at 20 inches for larger game,,or faster or further,, you would have to make up for the shorter power stroke with brute strengh, but thats ok if thats what you want,,
so I think thats why you see the longer draws, easier to get better cast and not as much practice to shoot accurately as a shorter bow,, I am not saying the short bow is not accurate,, just might take more practice to achieve the desired accuracy,,,