It's not.
It is said that "Assassin" (if it excists at all!) is a demo that is similar to Innuendo.
Similar to Innuendo doesn't mean it's a demo to Innuendo. Seaside Rendezvous is also similar to Lazing On a Sunday Afternoon. And Love Token is similar to Fat Bottomed Girls.
I doubtr that Assassin excists, and if it excists I seriously doubt it is similar to Innuendo. For all we know the 'demo'(?) starts with a drumroll or something.
There have been made many many many mistakes this way. For example someone heard Roger play a simple drum pattern in the soundcheck in Paris 2005 and posted on the internet that the band played One Vision in the soundcheck. While it was just Roger playing a simple drumpattern
Niek, your English is usually better than mine but in this case... "existing" has nothing to do with "exciting" :-)
As for One Vision, I'm not sure if it's the right example. If I remember well, I did hear Queen rehearsing One Vision in Leipzig (or was that Munich?) and it wasn't just a simple drum pattern.
Thanks Martin, I always mix these two words up :-)
As for One Vision, I wasn't at Leipzig, so I can't judge, but I believe this also happened in Paris. Or at some other show I saw.
But what I was trying to say is that some stuff can be mixed up easily.