Top-level field pushdown as implemented by SERVER-83441 doesn't depend on the number of fields. However, there may be very large predicates where it is prohibitively expensive to push down large number of fields (e.g. 10K fields). This is evidenced by test jstests/aggregation/query_limits_test.js.

This task will limit top-level field pushdown to a reasonable number of fields. If a condition exceeds this limit, no fields will be pushed down to the PhysicalScan.