> Can this be thought as bug in the spec? Is it appropriate to 
> put it in W3C bigzilla.

It's certainly not a bug - there was a conscious decision that the default
priorities could not reflect subsumption relationships in all cases. Some
might consider that the design could be improved, but it's the kind of thing
that one can't change retrospectively for reasons of compatibility.

Michael Kay
http://www.saxonica.com/