But TFA's estimate is perplexing because it is NOT a contrived scenario. We don't have marbles, we have some territory to cover. The territory isn't randomly distributed, we can't adequately randomly sample (presumably?).
It feels like the estimate could be wildly wildly off, in which case why estimate.
Regarding why estimate at all knowing they can be wrong ? Estimates are very useful for planning. Sophisticated models would also yield probabilities of over and underestimated, these combined with cost of over and underestimation errors are very useful for decision making.
See the German tank problem. Turns out the allied forces overestimated the number to f tanks left, still helped in planning.