It also says:
Both the house code and unit code may also reside in the same button
thereby creating a button for a specific X-10 module.
So it seems to suggest using a feature of the Pronto remote (adding multiple commands to one button) to send two separate messages rather than some mechanism of their protocol for combining them into one message.
That may be what I'm remembering. I had a TS-1000 and, later, a TSU-3000 (if my memory isn't too foggy).
I'll look again, tomorrow for CodeGen. I had put it on RemoteCentral but found so many people posting, and claiming credit for, codes it generated that I took it down.
The webpage that Laser currently hosts is a trimmed down, and static, archive. I asked them to host it after the Wayback Machine had problems when someone grabbed the
davehouston.org domain name. One of the attorneys involved in taking down Gawker is one David Houston (no relation) from down Texas way.