limitations of VOA?

Jun 4, 2005
Southern Ontario
Could it not be the case that there may be additions to a base oil which is not tested for by labs? So for example two different PCMOs could appear identical in a VOA but one may differ greatly than the other due to the inclusion of elements or compounds not test for? As well a VOA cannot determine the quality of the base oils used in the formulation? So again for example couldn't a synthetic oil and a mineral/nonsynthetic oil have identical add packs as seen in a VOA with the base stock being the difference? (or would the analyzed viscosity and flashpoint give it away?)