UITextView scrolling indicator cut off at top

Sample app

A collection view controller with list layout, 1 section and 1 row.

The cell's content view contains a text view.

class ViewController: UICollectionViewController {
    var snapshot: NSDiffableDataSourceSnapshot<Section, String> {
        var snapshot = NSDiffableDataSourceSnapshot<Section, String>()
        snapshot.appendSections([.main])
        snapshot.appendItems(["one", "two"], toSection: .main)
        return snapshot
    }
    var dataSource: UICollectionViewDiffableDataSource<Section, String>?
    
    enum Section {
        case main
    }
    
    init() {
        super.init(collectionViewLayout: .init())
        
        collectionView.collectionViewLayout = createLayout()
        configureDataSource() // more likely and automatically avoid unpleasant animations on iOS 15 by configuring the data source in the init rather than in view did load
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func configureDataSource() {
        let cellRegistration = UICollectionView.CellRegistration<UICollectionViewListCell, String> { cell, indexPath, itemIdentifier in
            let textView = UITextView()
            textView.font = .systemFont(ofSize: UIFont.labelFontSize)
            
            cell.contentView.addSubview(textView)
            textView.translatesAutoresizingMaskIntoConstraints = false
            NSLayoutConstraint.activate([
                textView.topAnchor.constraint(equalTo: cell.contentView.topAnchor, constant: 8),
                textView.bottomAnchor.constraint(equalTo: cell.contentView.bottomAnchor, constant: -8),
                textView.leadingAnchor.constraint(equalTo: cell.contentView.leadingAnchor, constant: cell.directionalLayoutMargins.leading),
                textView.trailingAnchor.constraint(equalTo: cell.contentView.trailingAnchor, constant: -cell.directionalLayoutMargins.trailing)
            ])
        }
        
        dataSource = .init(collectionView: collectionView) { collectionView, indexPath, itemIdentifier in
            collectionView.dequeueConfiguredReusableCell(using: cellRegistration, for: indexPath, item: itemIdentifier)
        }
        
        dataSource?.apply(self.snapshot, animatingDifferences: false)
    }
    
    func createLayout() -> UICollectionViewLayout {
        return UICollectionViewCompositionalLayout { section, layoutEnvironment in
            let config = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
            return NSCollectionLayoutSection.list(using: config, layoutEnvironment: layoutEnvironment)
        }
    }
}

Question 1

Can anybody edit the provided sample code so that the text view's vertical indicator inset is not cut off at the top?

Question 2

It seems to me that Apple has successfully implemented text views inside table view cells: can anybody provide Apple documentation as per how to do so?

What I've tried and didn't work

1. textView.verticalScrollIndicatorInsets.top = 30 // does nothing
2. Adding the text view to a custom view and the view to the cell's content view

textView.contentInset = .zero
textView.scrollIndicatorInsets = .zero  
textView.textContainerInset = .zero
textView.textContainer.lineFragmentPadding = 0

1. Centering the text view vertically and constraining its height to that of the content view with an 8 points constant to leave some padding
2. Constraining the top and bottom anchors of the text view to the cell's layout margins guide's top and bottom anchors

Constraint

I need the text view to have some padding from the top and bottom of the cell for aesthetic reasons.