We have not seen official guidance on this, but the LEEDuser expert consensus is "no." Each element of a building should be accounted for in either MRc1.1 or MRc1.2 and cannot be used twice. If a floor slab is reused and contributes to MRc1.1, it can therefore not also contribute towards MRc1.2. Even if it is used as a finish floor, that is not the same thing as reusing non-structural flooring under MRc1.2.