CFD tria mesh
 

I am using CFD tria mesh for several applications (Especially for External flow over some Automobiles...) without knowing it features.
I want to know why the CFD tria mesh is usually used for this application

Quads would work too. From what I understand... Historically, the files came as STL, Iges, etc, and those were as triangle (STL) or would have to be triangulated from the parasolid.

Quads are good for external flow because it requires less of them to render the surface, and external flow has lots of surface area to cover. Therefore, I would recommend using lengths of 2-10mm, and use "Best" method meshing to make Quad-dominant shell elements.

In general for CFD shell elements I use "best" method if I can, and it captures the geometry with least de-featuring.