...Because a UOA needs to be compared to a VOA in order for the analysis to be fully useful.
Oil analysis companies typically compare a used sample to the VOA of the [new] oil you specified was put into your engine.
lzb, thanks for the Romanian VOA and UOA links. Newer SN Ultra with the PurePlus GTL basestocks appears to use the same additive package, same moly, boron, calcium FM-AW-detergents, as they were using 2 years ago before GTL happened.
Unless, as some have said, they had used GTL in Ultra ever since it became SN.