Would it be possible to add an option to ignore player crafting in the production statistics? I'm really mostly interested in what my factory is producing, and the fact that I just hand-crafted a ton of belts shouldn't result in a spike in iron plate usage for example.

With how the API works, that'd be very tricky. Internally, it tracks a total number ever produced per faction. Mods that track production just ask "What am I at now? What was I at last time?" for each tracked resource so it's only doing a dozen calculations per tick. Registering an event listener to fire each time a player crafted an item (once per belt in your example) would significantly increase how much resources this mod takes up.

I see. Maybe it should be a feature request to the devs to provide building-production statistics per force as well as total?

Sorry if I worded that poorly. I believe that it is currently only available per force. To my knowledge, it doesn't track per source or handcrafted vs not beyond the internal count of "X things of all types combined have been crafted by hand" for a couple achievements. So it would be on the devs to add that before it could be used by modders.