Yes this appears to be a problem with all “in-topic links” - I have experienced that in another thread as well. If you click a link to another post within the same topic you cannot use the browser “page back” button to return to your start post (most probably because you are still on the same page).
If you opened the very topic on a new tab the “page back” button will remain inactive.
If you opended the topic within the same tab (by clicking a topic in one of the topic lists for instance) the “page back” button will immediately bring you back to the page or list where you came from.
I don’t know if you can call this a bug - I think it is annoying if you want to follow in-topic links in a very long topic - but at least one can see some reason for it (1 topic = 1 page).
No, still the same as before. You cannot use the browers “page back” button when the link you opened is within the same topic (for the browser the same page).