With product photography you want to be able to highlight/focus on certain aspects/functions/features of a product whilst throwing the rest out of focus. This is easier to do at higher apertures on a full frame camera. I also would recommend to be weary of shooting at f16 for it as most lenses lose sharpness significantly once the aperture is this closed, but obviously it depends on the product/s you are shooting and the desired effect.
The purpose of product photography is to show the product clearly in focus, not a wafer thin slice. At the close up distance typically shot this is difficult without stopping down significantly. I've done a lot of price photography and sell a lot of product stock, f/1 to f/16 was the norm for most.
Yeah, f/16 is not brilliant with diffraction but the alternatives are:
1) Use a PC/TS lens to control the focal plane so you can maximize the DoF.
2) focus stack a many images where you manually adjust the focus using a macro focus head. Compose in something like enfusion.
The former is expensive and the latter is time consuming. There is a 3rd option used in industry a lot:
3) use CG and have the whole thing a graphic from a good rendering package.
Typically uses for product photography are in brochures and websites so the ultimate resolution is not such a big deal and f/16 can work out fine on a budget.
The TS lenses are the common solution because they are quicker than stacking and double up as macro lenses anyway.
says to use f/22 to f/32