While I agree that the 65 to 70% success rate is a good benchmark, Taking the average AC of the challenge rating table is a fundamentally flawed method. Not only are some CRs practically non-existent the system also doesn't expect you to fight CR equivalent encounters.
It also fails to consider final accuracy rather than just your base attack. Barbarians get reckless attack which is a situationally huge accuracy booster. You'll notice almost all the class options that their main niche is hitting people with sticks they have something to increase their accuracy rather than just maxing their abilities. They also fail the consider intensity and frequency in relationship to the accuracy. My fighter can afford to miss a lot more often than a road because each individual attack is a much smaller portion of their impact.

This means maxing your primary attack stat is used to catch up to the classes that are supposedly have that type of stuff built in via other methods. Unfortunately it doesn't work that way because they failed in taking account basic human psychology and had a series of exceedingly larger numbers with a cap in the cap is going to instinctually be considered the goal. Regardless if they plan for the bill is going to be maxed or not it's a fundamentally flawed design that first removed that progression off the class and then added an "optional" rule to compete with it. It's technically agency but it's done in a way that just feels bad regardless of what you do pick. You either maximize your attack stat and keep with the status quo or fall behind and address a glaring weakness that is also entirely void of choice in and of itself because you don't get to pick when you make STs.

Well it's fun to talk about the theoretical differences between one or other it's also frustrating at the GM because you want players to make decisions and feel good about them even though sometimes they made the wrong one. It's missing all the feel-good failures well simultaneously stripping the sense of accomplishment from success.

I don't know if any of that made any sense so I'm kind of in a rambling mood today.