This actually seems like a throwback to jQuery mobile which had a similar way of doing full page transitions. I always thought that was ahead of its time.
Thanks for reporting! The website uses a mechanism to load subpages dynamically. I guess the closing and opening restores the history, but reloads the page from the server. The the content from layerjs.org is missing, but the history "thinks" its there. So we need to catch this...
I also found a bug (latest Chrome on macOS):
- open https://layerjs.org in a new tab
- navigate to https://layerjs.org/examples.html
- close tab
- reopen tab with cmd+shift+t
- pressing back will change the URL back to https://layerjs.org but the page will not change