the TBF is used to connect your MS to the MFS. It doesn’t care what kind of apps you’re running and what you(re downloading.
FRP, HTML, P2P, etc, everything will go through the same TBF.
In your case, you are downloading stuff, so you have a “long” DL TBF established. During this DL TBF, there will be a sporadic need to transmit UL data to the web server, to ACK the downloading (TCP ACK).
Those UL ACK will be transmitted through a UL TBF. It will be released after the UL ACK has been sent. And next one reopened after few seconds, for the next UL ACK.