你好，通过两种不同的方式显示PickerView，UI效果不一致

[MrCodeHauler]

UIView *contentView = [[UIView alloc] initWithFrame:CGRectMake(0, 100, 280, 300)];
contentView.backgroundColor = UIColor.whiteColor;
[self.view addSubview:contentView];

BRStringPickerView *stringPickerView = [[BRStringPickerView alloc]init];
stringPickerView.pickerMode = BRStringPickerComponentSingle;
stringPickerView.title = @"请选择学历";
stringPickerView.plistName = @"testData.plist";
stringPickerView.isAutoSelect = YES;
stringPickerView.resultModelBlock = ^(BRResultModel *resultModel) {
    self.educationSelectIndex = resultModel.index;
    self.infoModel.educationStr = resultModel.value;
};

BRPickerStyle *customStyle = [[BRPickerStyle alloc]init];
if (@available(iOS 13.0, *)) {
    customStyle.pickerColor = [UIColor secondarySystemBackgroundColor];
} else {
    customStyle.pickerColor = BR_RGB_HEX(0xf2f2f7, 1.0f);
}
customStyle.rowHeight = 60;
stringPickerView.pickerStyle = customStyle;

[stringPickerView addPickerToView:contentView];

通过以上方式，将PickerView添加至ContentView显示后，效果不一样，如下图

若是通过该方式[stringPickerView show]; 显示PickerView，效果如下 请问这是什么原因造成，还是设计如此呢，麻烦有空指教下，谢谢