Where are you finding documentation on the STi engine? Anywhere public?
AFAIK, it's pretty much the EJ20 STi block, only worked to make more displacement (prolly different stroke/bore).
It is similar to the block but there are some new and important differences.
It does sound like there is a lot in common with the 2.5 XT Forester and Baja turbo and the STi engine.
I suspect the revised block etc. was used in all of them.
I was reading a SCC on the newstand today and found even more errors (picture of 04 WRX interior labelled as STi, and they also said the DCCD uses a "clutch pack", which it doesn't).
So, my advice is to pretty much ignore anything you see in SCC.... or at the least the finer details.
For anyone who wants to know more about the mechanical part of the DCCD, I direct you to the Legacy H6/WRX Auto VTD documentation.