Pingbacks with anchors (that is #blah in the url)

I’ve just tried sending a pingback from

https://hearablog.com/site/7/Pablo-s-site-Music-for-coding#15

to my blog at

https://pupeno.com/blog/music-for-coding/

and it failed with error 17: The source URL does not contain a link to the target URL, and so cannot be used as a source.

I’ve tried again with

https://hearablog.com/site/7/Pablo-s-site-Music-for-coding

removing the anchor, and it worked. Why is WordPress claiming the other url not to have the link, it clearly does. Is this a bug in WordPress? The pingback spec clearly shows this should work. Is this some general behavior I should expect of other sites as well?