Lead programmer for the first two Shenmue games, Tak Hirai, has shared some insights into the development of the games in some tweets today. Since they were in Japanese, we have provided English translations.
When asked about the legendary Shenmue Saturn version, he responded:
"The rendering was created by me with much effort. The program was quite revolutionary with a branchless structure. The source code - as well as the graphics - is something I'd love to show the coders of the day".
He also shared a photo of himself during development of Shenmue around 1998 / 1999 at age 27. As lead programmer on the project, Tak said that his dev environment was sizeable but the air conditioning didn't work properly (note the paper fans ready for use!).
Regarding the Shenmue Saturn version, Tak Hirai's prefaced his comment with a light-hearted note that he thinks the "statute of limitations" (on discussing the Shenmue Saturn version) should have expired by now - so hopefully we will be able to hear more from him in future on this topic.