My understanding of the Mavic hubs is this:
Mavic hubs need a special Mavic spacer for all non-mavic Cassettes. For example, a 9 speed cassette on a non-mavic 9-10 speed hub would need no spacer, but on a Mavic hub, it will need that Mavic spacer.
A 10 speed hub would need a little spacer on any 9-10 speed hub. If it's Mavic hub, it will need that little spacer IN ADDITION to the Mavic spacer.
Hope that makes sense and is an accurate understanding.