This has been done to death on here before - try the search function. But broadly speaking, you are right; the issue is whether a VMC IFR procedure is a 'practice' approach. IFR in VMC OCAS you are of course responsible for see and avoid; it's up to you whether you think you can do this while conducting an IAP.
In real IMC once you went visual you would probably continue visually, heads up, but when doing an approach for practice you would probably remain on instruments even when visual. That being the case you are in danger of collision with VFR traffic unless you are in class D or above where separation is provided by the controller.
Tim