I'm asking if something changed in 2.1.x from 2.0.x that might not be in
the swapon man pages.
You might want to check if the init scripts are invoking plain swapon,
if it is you can check to see if the priority is being specified
explicitly. I don't think swapon checks fstab to get this
information.
Next step is if mount is being used, make sure the version of mount
knows about the priority argument in the fstab.
Nothing has changed between 2.0 and 2.1 to my knowledge which could
change this, at least as far as I can tell.