Good News!
Although Wolfram hasn't advertised it, it looks like the formatting on Symbol pages was fixed in 13.1. The info button on the symbol hover drop-down is still squirrely, but it's livable with the workaround above. I had to rebuild some pages, since:
- Metadata fields have changed (it's simplified)
- Metadata has moved to the bottom of the Custom Function, Reference, Tech Note page template.
- Tutorials are now officially, and consistently, Tech Notes in all reference fields (but still stored in the Tutorials subdirectory of the paclet documentation).
Most of this was just a copy and paste from my old pages in the old format, which didn't build well. Now, I can't tell the difference between my custom symbol pages and Wolfram's.