I don't know if this is helpful, but this 2003 research estimates about 6 animal deaths per acre of agricultural harvest, or about 7.3 million animals.[1] That puts it about on par with industrial animal consumption. But granted it seems much more difficult to have accurate estimates.

I think part of the problem is that most people in industrialized economies are extremely far removed from the food supply. I don't think it's super common, but also not unheard of for deer (especially fawns) to be killed by harvesting machinery as they bed down in fields. Considering hunting a deer may yield 60-70 lbs of meat, it might be possible to claim that reduces total animal deaths. Now I don't know how you'd arrive at a final number because most people are omnivores and still eat plants, but I don't know if I'd immediately dismiss their claim as absurd.

I see from your profile that you work in the farming machinery business so I'd be curious if there are any specific mitigations you would consider to alleviate this problem?

[1] https://link.springer.com/article/10.1007/s10806-018-9733-8