It is often the best way when on a budget. Legit 3D blur is computationally expensive. Once I was like "hmmm, so I'm rendering out only about 200,000 polys, 12 second shot with some detailed maps. I have 28 hours till delivery. Oh. this render will take 34 hours. Time to do post blur instead. Ah ha! 12 hour render! Now I can do a second render if this one has any issues."

But yeah, in an ideal world, we'd be able to do everything with beautiful 3d blur....

What you're describing (IF the move is rock solid otherwise), definitely sounds like shutter phase/opening issue. Esp. if it's heavily noticeable on jerky moves. Luck to ya!