NSMutableAttributedString from HTML styles li bullets and numbers erroneously

Question

I have added a convenience constructor to NSMutableAttributedString to accept a String of HTML and a font.

extension NSMutableAttributedString {

    // Convert HTML, but override the font. This copies the symbolic traits from the source font, so things like
    // bold and italic are honored.
    convenience init?(html: String, font: UIFont) {
        guard let data = html.data(using: .utf16, allowLossyConversion: true) else {
            preconditionFailure("string->data can't fail when lossy conversion is allowed")
        }

        do {
            try self.init(data: data, options: [.documentType: NSAttributedString.DocumentType.html], documentAttributes: nil)

            enumerateAttribute(.font, in: NSMakeRange(0, length), options: .longestEffectiveRangeNotRequired) { value, range, stop in

                guard
                    let currentFont = value as? UIFont,
                    let newDescriptor = font.fontDescriptor.withSymbolicTraits(currentFont.fontDescriptor.symbolicTraits)
                else {
                    return
                }

                let newFont = UIFont(descriptor: newDescriptor, size: font.pointSize)

                addAttribute(.font, value: newFont, range: range)
            }
        } catch {
            return nil
        }
    }

}

I'm running some HTML using ol and ul tags through this and placing them on a label.

    let html = [
        "<ul>",
            "<li>not a link</li>",
            "<li>",
                "<a href=\"https://www.google.com\">link</a>",
            "</li>",
            "<li>",
                "<strong><a href=\"https://www.google.com\">bold link</a></strong>",
            "</li>",
            "<li>",
                "<em><a href=\"https://www.google.com\">italic link</a></em>",
            "</li>",
        "</ul>",
        "<ol>",
            "<li>not a link</li>",
            "<li>",
                "<a href=\"https://www.google.com\">link</a>",
            "</li>",
            "<li>",
                "<strong><a href=\"https://www.google.com\">bold link</a></strong>",
            "</li>",
            "<li>",
                "<em><a href=\"https://www.google.com\">italic link</a></em>",
            "</li>",
        "</ol>",
    ].joined(separator: "\n")

    guard let string = NSMutableAttributedString(html: html, font: UIFont.systemFont(ofSize: 18)) else {
        fatalError()
    }

    label.attributedText = string

When I place this into the label the bullets and numbers are bold, italic, and blue links, even though the strong, em, and a tags are inside the li.

I'm guessing this is a bug in NS(Mutable)AttributedString and am prepared to file a radar, but I wanted to see if StackOverflow can find a bug in my code first.