I don't know that it is any rarer. I think it is a combination of a couple factors.
1. There is still a ton of 1994 Stadium Club Series 2 unopened.
2. Ozzie had a huge collector following back in the day and I'd bet most are locked up in collections that haven't seen the light of day in a few years.
That said I'm only about 80% sure I have one. I'm going to have to check when I get home this evening. I know I have the Gold Foils of all his cards but not sure on the FDIs.
This seems to be a trend with Ozzie cards actually. I've known a few different sets where multiple guys got down to just needing one card for years and it was Ozzie.