All broom boy did was levitate a broom. It’s been implied Luke was subconsciously tapping into the Force which helped his piloting skills on Tatooine before he was even aware of it. Ditto for young Anakin. That’s not instant knowledge of the Force.

When the Jedi went looking for Force sensitive kids, I imagine levitating small light objects is one of the tells. Another child might display precognitive abilities. Still another might be a great pod racer. They would be pretty hard to find otherwise.