const newSelectionModel = apiRef.current.getPropagatedRowSelectionModel(propRowSelectionModel);

const getPropagatedRowSelectionModel = (inputSelectionModel) => {
  // No check for exclude model type! ❌
  if (!isNestedData || !applyAutoSelection || ...) {
    return inputSelectionModel;
  }

  const propagatedSelectionModel = {
    type: inputSelectionModel.type,  // 'exclude'
    ids: new Set(inputSelectionModel.ids),  // Set([1]) - EXCLUDED rows!
  };

  const selectionManager = createRowSelectionManager(propagatedSelectionModel);

  // Iterate over EXCLUDED row IDs ❌
  for (const id of inputSelectionModel.ids) {  // id = 1 (Thomas)
    findRowsToSelect(  // ❌ Wrong function for excluded rows!
      apiRef, tree, id,
      props.rowSelectionPropagation?.descendants,  // true
      props.rowSelectionPropagation?.parents,  // true
      (rowId) => selectionManager.select(rowId),  // ❌ Removes from exclude set!
    );
  }
};

// In gridRowSelectionManager.ts
select(id) {
  if (this.model.type === 'exclude') {
    this.model.ids.delete(id);  // ❌ Removes from exclude set!
  }
}

{ type: 'exclude', ids: Set([1]) }
// Meaning: "All selected except Thomas"

{ type: 'exclude', ids: Set() }
// Meaning: "All rows selected!" ❌

// In selectRow (lines 294-302)
} else if (applyAutoSelection) {
  findRowsToDeselect(  // ✅ Correct function
    apiRef, tree, id,
    props.rowSelectionPropagation?.descendants,
    props.rowSelectionPropagation?.parents,
    (rowId) => selectionManager.unselect(rowId),  // ✅ Adds to exclude set
  );
}

{ type: 'exclude', ids: Set([1, 2, 3, 4]) }  // ✅ Already complete!

const getPropagatedRowSelectionModel = (inputSelectionModel) => {
  if (
    !isNestedData ||
    !applyAutoSelection ||
    inputSelectionModel.type === 'exclude' ||  // ← NEW: Skip for exclude models
    (inputSelectionModel.ids.size === 0 && inputSelectionModel.type === 'include')
  ) {
    return inputSelectionModel;  // Return unchanged
  }

  // Propagation logic below only runs for include models now
  // ...
};