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.
Yeah I get all that. The problem I find with it is that Luke clearly struggled to get his lightsaber, far older than broom boy who pulls the broom towards him without a care. Also Reys first ever lift with heavy objects (the boulders) is done with ease. That was deffinetly not something that Luke taught her. Rey did everything that Luke did throught the whole OT in just TFA. Then we are to belive that she is going to Luke for training?