cell.defaultContentConfiguration() vs cell.textLabel

For a tableView: I try to change my code from using cell.textLabel to cell.contentConfiguration, we can't get the same result as before (using cell.textLabel), I like to keep the row heigh at 20, the old code display nicely, but the new code won't be able to show it at all unless I use row height 40. Here's the code:

import UIKit

var fruites = ["Apple","Orange","PineApple", "Water Melon", "Banana"]

class ViewController: UIViewController {
    @IBOutlet weak var tblTableViewA: UITableView!
    override func viewDidLoad() {
        super.viewDidLoad()
        tblTableViewA.dataSource = self
        tblTableViewA.delegate = self
    }
}

extension ViewController: UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return fruites.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "CellA", for: indexPath)
        let fruit = fruites[indexPath.row]
        // New code does not display right, content does not display properly like old code. when row height = 20, it won't even show.
        /*
        var content = cell.defaultContentConfiguration()
        content.textProperties.adjustsFontSizeToFitWidth = true
        content.text = fruit
        cell.contentConfiguration = content
        */

        // Old code works perfect
        cell.textLabel?.adjustsFontSizeToFitWidth = true
        cell.textLabel!.text = fruit
        return cell
    }

extension ViewController: UITableViewDelegate {
    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat
    {
        return 20 //CGFloat(20)
    }
}

Thanks in advance!