Yes, I left it out when I first implemented Asciidoctor because I didn't think it was needed (it felt very 90s and to be honest, there are parts of AsciiDoc that deal with legacy needs).
I've been pinged about this from several folks and now realize it needs to be supported.
In the interim, you can use a passthrough:
Btw, if you have questions about compliance issues in Asciidoctor, be sure to consult the issue tracker. We're trying to be good about collecting all compliance issues there, so you might save yourself time by discovering you are not alone if you are facing an issue.