Not sure what QPI website is you've mentioned.
All oils, conventional and synthetic have some nitrogen and sulfur.
Sulfur is naturally present in conventional oils depending on their level of refinement.
Additive components such as ZDDP and detergents will raise the sulfur content of both conventional oils and synthetic oils.
The nitrogen comes primarily from the anti-oxidants.
So sulfur and nitrogen both contribute to the "well-being" of the formulated oil package.
Below is a thread that discusses the actual additive chemistry: Chemistry of Additives
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