They were never really supposed to be interoperable with pingback from what I can tell, see the reasons here[0].

You're right in the sense that it's a classic case of <insert XKCD standards comic here>, but FYI there is a pingback to Webmention converter now[1].

[0]: https://indieweb.org/Webmention-faq#Why_webmention_instead_o... [1]: https://webmention.io/#forwarding