I have translated countless interviews and articles from Japanese sources over the past few years on Sega's history, and yes, the whole issue is full of ridiculously inaccurate information.

Here's a thread of some recent info I uncovered about the 32X, for example:

https://www.sega-16.com/forum/showthread.php?35945-Japan-exe...

I'm also not sure what you are talking about when you say Japan refused to share information on internal prototypes. Is there actual evidence of this refusal?