The 93 European Tour was Spain, Denmark, and the UK as far as we know. The 91/92 European tour was Germany, Switzerland, Lithuania, Poland, Czech, Austria, Spain, UK, Belgium, Netherlands, and Ireland. And there are more than just rumors to support that, if you'd like any specific proof, let me know and I'll show you.
I don't think it was 93, it was 91 and 92 when they toured Europe and played those places. They were tiny shows (many just in houses or squats) played when Green Day was unknown in Europe and before people filmed shows using phones or there was the internet, so it doesn't surprise me there aren't more accounts or recordings, even from the UK there's only footage of a couple of shows. It definitely happened, the band's given detailed accounts of touring round the US in a crappy van and then taking a trip to Europe to do the same, the lack of reports of it from people who were there is to be expected under the circumstances rather than being suspicious.
I agree, that was a bizarre choice. When I saw that Dookie was #2 I couldn't imagine what could have beaten it. I still don't see how Enema of the State beat it.