Not All OEM matey,
I work for BASF the chemical company and I'm in the Automotive coatings division
We are the market leader in the automotive coatings industry, lots of solid colour solvent bourne paints we supply today are a single coat technology (they don't use a clearcoat finish)
The gloss finish is part of the paint (the chemicals/raw material that create the gloss are built in)
Early Toyota white 040 (like my 94 faff) is a single stage topcoat
The current solid white on all Nissan's produced in Sunderland (Qashqai, Note, Juke) are a single stage topcoat.
But for Sonic's Astral Black it does use a Clearcoat after the basecoat as with all metallic and pearls