I'm aware; as you say though, sadly, it's unobtainium (and non compliant, so it's guaranteed to have compatibility problems with some devices and drivers).
Real transaction translators in USB 2 work with host cooperation and specific support for USB 1 devices in the protocol, while this is trying to do transparent protocol conversion. Sadly, due to USB's design, this runs into the same corner case problems as any other kind of tunneling.
The main problem is the polled architecture. Host asks device for data; translator has to reply immediately so it has to say there is no data yet and ask the device for data. Translator buffers data and delivers it to the host the next time it asks. Except the host is allowed to never ask, again. Now the translator has data it has to drop on the floor. Not good. And this all requires heuristics to decide what to do. It's a mess.
