UIButton insets bug for multiline attributed title - swift

Question

I want to design a button respecting these rules:
Content horizontally centered
18px margin on both side of the content
10px between image and title
Title will wrap on multiple line if needed
Use attributed title
I have a working solution using:
button.setTitle(title, for: .normal)
Result:
But I can't figure why it's not working if I use:
button.setAttributedTitle(NSAttributedString(string: title), for: .normal)
Result:
It does not respect the 10px and 18px insets. Also note that the problem only occurs when the title becomes multiline.
Here is the playground I used to pinpoint my problem:
//: Playground - noun: a place where people can play
import UIKit
import PlaygroundSupport
extension UIImage {
class func imageWithView(view: UIView) -> UIImage? {
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.isOpaque, 0.0)
view.drawHierarchy(in: view.bounds, afterScreenUpdates: true)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image
}
}
class ActionBarView: UIView {
// MARK: Properties
private var icon: UIImage?
private let stackView = UIStackView()
private let proposeButton = UIButton()
private let declineButton = UIButton()
// MARK: Initialization
override init(frame: CGRect) {
super.init(frame: frame)
designView()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
// MARK: Design
private func designView() {
designIcon()
designStackView()
designProposeButton()
designDeclineButton()
}
private func designIcon() {
let image = UIView(frame: CGRect(x: 0, y: 0, width: 20, height: 20))
image.backgroundColor = .magenta
icon = UIImage.imageWithView(view: image)
}
private func designStackView() {
stackView.addArrangedSubview(proposeButton)
stackView.addArrangedSubview(declineButton)
stackView.distribution = .fillEqually
stackView.spacing = 1
addSubview(stackView)
stackView.frame = frame
}
private func designProposeButton() {
design(button: proposeButton,
icon: icon,
title: "Propose a task")
}
private func designDeclineButton() {
design(button: declineButton,
icon: icon,
title: "Decline")
}
private func design(button: UIButton, icon: UIImage?, title: String) {
button.contentEdgeInsets = UIEdgeInsets(top: 0, left: 18, bottom: 0, right: 18)
button.titleEdgeInsets = UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 0)
button.imageEdgeInsets = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 10)
button.titleLabel?.backgroundColor = .green
button.imageView?.backgroundColor = .orange
button.backgroundColor = .white
button.setImage(icon, for: .normal)
// button.setAttributedTitle(NSAttributedString(string: title), for: .normal)
button.setTitle(title, for: .normal)
button.titleLabel?.lineBreakMode = .byWordWrapping
}
}
let view = ActionBarView(frame: CGRect(x: 0, y: 0, width: 320, height: 44))
PlaygroundPage.current.liveView = view