NX Mass properties calculates the total weight of the assembly though the empty reference set is set.

The updated weight is considering the weight of all the bodies present in "Empty reference set" along with models present in SOLID reference set.

The Reference set selections in the Assembly Navigator affect display simplification only and do not affect mass properties calculations at all though it is changed in (Customer default ->Gateway -> Mass/Material -> Miscellaneous-> Mass Properties reference set precedence->User defined reference sets)