Parity error between nominations and candidates?

Hi all,

I fear I've forgotten the answer to this, so here's a stupid question: why are
some nominated people not candidates in the election even if they've got two
nominations?

Is it because the candidate has to accept the nomination, and those candidates
haven't accepted the nomination?

For example, Michael Still was nominated for the committee by two people, but
isn't a candidate?

It would be good for any future voting system that Linux Australia sets up to
include information like that to help idiots like me understand the parity
error :-)

Thanks in advance, and have a good holiday,

Paul