Following SERVER-132742, find now marks shed-eligible from inside getExecutorFind()/getExecutorFindDeferredEngineChoice() (past the express decision), while aggregate, getMore, and distinct still mark unconditionally at the top of run(), so the opt-in decision lives at a different layer depending on the
  command. We should investigate whether these could share a single, more uniform mechanism for the eligibility decision instead of each command implementing its own place to mark, while still preserving instruction counts on the fast path.