anchor.diff:    // allOnPageSelected and allAcrossPagesSelected, but it turns out to be
     // ambiguous and does more bad than good.
     bool get allAcrossPagesSelected =>
  -      supportsSelectAll &&
  -      (_allSelected ||
  -          (_selectedCount > 0 && totalEntitiesCount() == _selectedCount));
  +      _allSelected ||
  +      (_selectedCount > 0 && totalEntitiesCount() == _selectedCount);
   
     @override
     void selectAllAcrossPages() {
       if (_allSelected) return;
  -    assert(supportsSelectAll && supportsMultiplePageSelection);
  +    assert(supportsMultiplePageSelection);
       bool wasEmpty = isEmpty;
       _allSelected = true;
       if (wasEmpty) {
  
positive.code:       _totalEntitiesCountController.stream;
  
    @override
    CountGetter entitiesOnPageCount = _noCountGetter;
  
    @override
    IsIndeterminate isIndeterminate;
  
negative.code: 
    @override
    bool get isPageSelected =>
        selectedCount > 0 && selectedCount == entitiesOnPageCount();
  
    @override
    void onRemove(T entity) {
  