I turned on the VPN, started downloading Ubuntu as a test and while it had good connection and speed I turned off the VPN to check the binding was working, and it did eventually stop downloading but it didn’t stop right away. Took around 30 seconds to it completely stop and until then it just kept slowing down, but still downloading.
There is a residual speed that is still shown… but iirc there’s also a symbol for the connection (sometimes red, sometimes yellow, and sometimes green).
After binding and turning off your vpn, that symbol should immediately turn red (for no connection).
What you’ve described is totally normal btw, just the buffer clearing. That said, how both of the aforementioned sites work is to generate a tiny tiny “unique to you” torrent file which you then manually add to your torrenting software of choice, then the site will immediately show you what IP address that torrent is being downloaded from.
It’s a rolling average to “smooth” out the numbers. Otherwise you would unhelpful flickering between 0B/s and 20MB/s whenever one piece is fully loaded.