Even FreeCAD has some fundamental differences (and lack of functionality) between it and other mainline CAD programs.
Hopefully someone with more knowledge and experience than me can hop in and explain more, I'm just a CAD user, not a CAD kernel developer.
3D modelers like blender (or even OpenSCAD) work with a bunch of triangles - there is often not some higher level representation of the geometry. You could put a drill hole in a part, but it ends up as just a ton of triangles that approximate that drill hole, vs. a file format which semantically encodes "there is a cylindrical drill hole at this location, with this vector direction, and this radius".
That's what things like BRep (Boundary Representation) and STEP files give you is that semantic data which describes the part "here are the edges, faces, dimensions, etc.", vs. "here's a bunch of triangles, good luck machining this"
This is very much how I internally understand it and explain it to people, yes!
It is a good analogy for e.g. why it's often a challenge to get something milled with a CNC when you only have an STL file.
STL is like a PNG line drawing: it can be high quality, but it's not describing the drawing. STEP is like SVG: it's more effort to render it, but it contains the instructions to draw it.
Edit: Along with the fact that blender has a lot of non destructive workflow steps (that usually get baked out into the "bitmap", to further your analogy)
I think with enough plugins and customizations, you _could_ twist blender into something that resembles a CAD modeler, but it's really an uphill fight compared to selecting tools which were designed with that goal in mind from the start.