I had to do some product shots recently. I was using a professional Nikon AF lens, close to the focus limit.

With AF the focus was more miss than hit. I couldn't get a really sharp result until I turned off the AF and focussed by hand.

The focus location was right on the object, with a focus spot parked on top of it, so I wasn't trying to focus on some random thing elsewhere in the frame.

I've noticed this before with AF - it's very much not perfect, and if you want an extra level or two of sharpness it's best to focus manually.

I'd guess it depends on the algorithms in the camera too.