I have more info to add:
- Ctrl-Shift-R still does not cause the changes to appear
- Clearing site-specific data this way, also does not work (which afaik is the same as a hard refresh)
However…opening the Publish site in a private browser window does make the changes appear - immediately after publishing.
So, I am not sure how this is possible, but it appears that whatever cache is being used to store the content somehow survives hard refreshes, but not private windows. (?)