TUSB8020B: Trying to understand the functionality of the TUSB8020B device

I need to understand how this part works. It was suggested to me that this part would allow a SS device and a HS device to be connected to the TUSB8020B device at the downstream ports and then combine these into a single SS interface at the upstream port. Looking at the datasheet it appears to me that this is not the case and that the TUSB8020B device allows both a SS data path and a HS data path from two different downstream ports to be transferred at the same time at the upstream port. However, I am not sure I understand how this works since the USB protocol requires a HS connection to be valid in order to enumerate to SS, at which point the HS interface is no longer used and the data path is pushed to the HS interface. PC hardware supports HS/SS on a single port but not at the same time since these interfaces share the same hardware features such as FIFO's and DMA engines. I thought that maybe the TUSB8020B device would allow two different devices to be connected using on cable at the upstream port and then at the PC side the cable would be broken into two different connectors, one for HS and one for SS. But I do not see how this would work. Can someone please supply more information on how this part works? Out interest in this device is to provide both a HS data path and a SS data path using one cable for two different downstream devices.