Rules are simple, you can’t tackle unless you’re tackling the ball, outside of a shoulder to shoulder physical contact is not allowed really (by rule book)
Shouldering not allowed in the rule book.
The way is is being refereed at all levels (I watch a lot of ladies football) is that the ball carrier tends to be penalised if they are travelling at pace and a defender who runs into their path collides with them and falls over. It is interpreted as charging , even when the ball carrier has both hands on the ball, and has clearly no interest in taking contact. Would have no issue when a player puts a hand out or leads with elbow. But that’s often not the case. Meath had two given against them early in the game on Sunday. Donegal had a ludicrous one given against them in the last minute of semi final when going for what would have been the winning goal. Meath back ran in to the path of the Donegal forward, caused a collision , fell over and got a free out.