Don’t confuse bonded ADSL with load balanced ADSL. Bonding involves splitting data up at the packet level, and distributing it across all the available lines on site. The data is then cleverly put back together again before being sent out to the internet, or to another site within the same network.
This works both ways, for uploading and downloading. Load balancing ADSL lines means individual data sessions are put over separate lines. You will never get the top speed of a bonded ADSL connection, and each line will have a different IP address, making hosting and resiliency nigh on impossible.