The CDC have not found it in any nicotine cartridges. The CDC have also not found the substance in the lungs of any vape users who didn’t use THC products. There are also jurisdictions which have reported finding it in 100% of seized THC cartridges.

It was found in carts that had THC and nicotine combined. That makes it about as much as a nicotine additive as a THC additive, if we are using the incredibly low standards of "found in coexistence with substance sometimes" as the definition of additive.