I assume this is the person you're talking about? https://segaretro.org/Hideki_Watanabe
Looks like he stopped making anything for Sega around 2001 (publicly at least) so that lines up. But there are a huge amount of patents credited to a Hideki Watanabe (could be multiple people with the same name) including some odd arcade-game related ones: https://patents.google.com/?inventor=Hideki+Watanabe&oq=Hideki+Watanabe