Autofocus on nikon macro lens?

I have a nikon macro lens that has a switch to turn the lens to M (manual) or M/A (manual/automatic focus). The instructions say that when switched to M/A, to use the manual focus you have to lightly press the shutter button while at the same time manually focus the camera, but it seems to manually focus without me having to lightly press the shutter button when switched to M/A. Does anyone know why the instructions say to press the shutter button at the same time as manually focusing in M/A?

Why don't you just use the lens in the Manual Mode when you are using the lens as a macro lens?

When shooting at image to subject ratios in the 1:1 to 1:4 range, focus is achieved by moving the camera, not focusing the lens. If you focus using the lens, your image to subject ratios changes.

M/A is auto-focus with manual over-ride. Yes, you can focus without half-pressing the shutter release, but if you DO that, the camera will try to adjust the focus when you press the shutter button down. If you do the half-press and then re-focus, it will not try to adjust the focus when you finish depressing the shutter release button.

If I'm NOT doing a critical focus for macro, I half-press for the camera's opinion and then, while holding the button half-way in, I move back and forth until the part that I really want in sharpest focus looks good. Then I finish pressing the shutter release button.

If I'm doing something critical, I use a tripod and manual focus. If you were a freak about this, you would have a tripod with a micro-adjustable head so you could make small camera position changes to get the focus right while maintaining your 1:1 (or whatever) magnification, as fhotoace has suggested.