I have 2 cards and a tag (bought together with the reader).
When I place all three near the antenna, only one (and always the same) of the cards gets recognized (probably that would be the first one selected by anticollision algorithm).
That’s not order-dependant.
And the multi-card flag doesn’t get set.
PS: on the wiki page there’s only the name of the file with the protocol description, but the file is not there. It’s on neophob’s blog.