 Another way to see that the conditionals are false is to notice that properties everything has necessarily and ones that nothing can possibly have supervene, with the same sort of necessity, on any property whatsoever. (The fact that the necessary and the impossible supervene on anything and everything arguably poses a problem for attempts to use supervenience to define physicalism. See  Section 5.4.)  The property being self-identical supervenes on the property being an antique; the property being both a kangaroo and not a kangaroo supervenes upon the property being dusty. The reason is simple enough. No two things can differ with respect to either necessary or impossible properties, period; thus no two things can differ with respect to such properties without also differing with respect to B-properties, for any property set B. Nothing can be both a kangaroo and not a kangaroo, so no two things can differ with respect to that property, and thus no two things can differ with respect to that property without also differing with respect to being dusty, or being purple, or being a steam engine, etc. But it is not the case that being both a kangaroo and not a kangaroo is ontologically dependent upon being dusty, or that being dusty grounds being both a kangaroo and not a kangaroo. Being dusty has nothing to do with it at all.