Headshake: Just from my observations, removing fans (in flower) makes the plant more susceptible to stress, becomes a missing component that regulates heat and moisture, the nutrients are no longer locally available and must be constantly re-supplied to make up for the loss, there's time lost healing wounds...and how much is lost in overall yield? Have you done a side-by-side? (curious, not accusatory )

Other than removing leaves because of something you've sprayed on 'em and it's killing the plant, I can't see removing the healthy fans on purpose.

In veg, as long as you give ample time for recovery prior to switching to 12/12, tiz almost an anything goes deal. From fimming to topping, to high-stress bending and scrogging. Once 12/12, best to let 'em do their thing.