Practice that beats theory is just a new theory, so practice can't beat theory, it can only beat out of date or simplistic theories.
I understand what the saying means, but it gives people so many bad ideas about the value of theories and science or how to work with them. In practice you start out based on general and overly simplistic theories, and then expand the theories in the direction you need to solve your problems, and then that creates a new theory you base your practice around.
Wandering around willy-nilly without testing isn't good practice, while going deliberately with lots of testing and logic is what we mean when we talk about theory.
Emerging practice is the ground theory hasn't covered yet.
You are correct, though, in that if you want to make these practices more useful and grow your overarching theory, they absolutely must be approached with lots of testing and logic. The trick is knowing where it's most important to do this & when.
Many areas of practice are left untouched by theory because there is no obvious compelling benefit.
There can still be a difference between practise and a(n insufficient) theory without there being a new theory superseding the old one. A lot of historical developments take this shape: we discover something not predicted by the theory we though would explain it, work on it for a while, and only later do we find the new theory that explains also the novel thing.
For practise to be condensed into theory requires predictive power, and not all differences between practise and a theory are predictable -- yet.
That said, I agree with your overall point. If one finds a difference between practise and theory, it's because one tried to use the wrong theory for the situation at hand.
I understand what the saying means, but it gives people so many bad ideas about the value of theories and science or how to work with them. In practice you start out based on general and overly simplistic theories, and then expand the theories in the direction you need to solve your problems, and then that creates a new theory you base your practice around.
Wandering around willy-nilly without testing isn't good practice, while going deliberately with lots of testing and logic is what we mean when we talk about theory.