Spring Unrendered asciidoc headings in reference documentation

See for example https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-websocket

It contains

= Introduction to WebSocket

which is not rendered as a heading.

Comment From: sbrannen

This is due to the use of {chapter} in the IDs.

websocket-intro.adoc attempts to use dynamic IDs such as [[{chapter}.websocket-intro]]; whereas, web-uris.adoc uses dynamic IDs such as [id={chapter}.web-uricomponents].

The latter works (at least in this particular arrangement).

I noticed the difference previously while working on a different issue and wondered if it was problematic, but I forgot to follow up on that. Now we know!