Are you running the update in the disposable or the template ?
It takes the Tor version from whatever the template has so if you update it there it will be updated in disposable. Run the Tor browser updater in the whonix ws template and then shut down the template. Then disposables will start with new version
If you want to only update in the disposable then I imagine you can run below in cli and then relaunch Tor browser from the cli