You can get away with only using the count and the maximum because of the assumption of uniformity. Once that assumption goes away, the assumption no longer works.

If earlier tanks are much more likely to be captured, then the number of samples will be exaggerated compared to the maximum number seen, so you'll underestimate production. If earlier tanks are much less likely to be captured, then the number of samples will be smaller compared to the maximum, and you'll overestimate.