Yes it is accepted, but it all depends on the project.
If you are starting a project from scratch and the shape is not defined or very open to interpretation, then I would recommend sketching so that you don’t get bogged down.
If the project requires minimal tweaks, or is a very geometric design, or proportions are crucial then I wouldn’t be afraid to start with CAD.
A good example is a medical cart. It had a bunch of components coming together and a lot of fabricated parts rather than injection molding. I created a 3D CAD model and rendered it and then sketched on top of that modifying the extrusion profiles, adding details, sketching in the few molded parts, etc.
Whatever tells the story more efficiently.