You have no idea how sophisticated a 10 year old kid can be with fouls.It is absolutely a foul, yes, 100% of the time, always. I agree the ref was incorrect. What I am telling you are some of the reasons for why the non-call, that's it. If you are in a close game in a youngers match refs will always call games very very loosely because of the nature of the youngers game. Remember these kids aren't of the age to have the intent to foul. Hold up play? Physical play? Sure. But I can absolutely guarantee that the Beach CB did not go into that collision thinking "I'll take the foul here". They just aren't of the age to be able to make that decision.
I have only very very very rarely seen a ref call a youngers game tight. It just doesn't happen and more parents need to understand this. Youngers refs do not want to influence the game. How many times have you seen a youngers team ship a goal because a line judge misses that last touch before the ball goes out? That's on a decision that they are forced to make. If you got refs calling tight matches on the younger side against kids who are terrifically uncoordinated when they tackle, games would have scorelines of 30-1.
10 year old girls, at the highest level, can absolutely figure out what is a foul, what the ref will call, and make a conscious decision to blast into another player when they think the ref is a pushover.
I’ve watched my kid do it, and I’ve had that exact discussion with her on they way home. She can clearly articulate what the rule is, what the call should have been, and the missed calls early in the game that told her the ref would let it go.