Hot take: People are different.

Just because *you* don't notice a difference between crank arm sizes doesn't mean that is universally true for everyone. I had some pain issues that were eventually alleviated, in part, by changing crank arm length. (There's a lot more to it than just that but that's the short version.)

So for *me*, I can definitely tell a difference in crank arm length because of my unique physiological circumstances.

But I also don't tell other people, who say they don't notice a difference, that they are wrong.

See how easy it is?