The answer to your question depends on a lot of factors. What's the strain/phenos resistance to stress? How is the general health of the plant? Also how often one prunes and how much they prune back can affect the plant. I think a safe rule of thumb for pruning (namely the fan leaves and what will becomes larfy popcorn) is to never remove more than 20% of the plant in a given session and giving plenty of time to recoup before the next pruning. In regards to defoliation and pruning vs. letting nature take it's course, one should look at the grape vine. It's best and most flavorful yields require more than proper nutrient and watering (or lack thereof) to be achieved, and the vine itself must be put under some demand to work the plant. If the vine was to simply "go to seed", aka reproduce itself through seed, the profile of the grape wouldn't matter, and obviously, letting nature take its course would be the preferred method. But for the purpose that we use grapes, the better crop is not grown without pruning and stress. This includes timing, putting a load on the plant to drive the roots deeper, pulling nutrients from deep down enhancing the flavor and preserving the vine in times of drought. Yes, before a naysayer says anything, it's apples to oranges (well, grapes to buds), but the example stands to show that not all is perfected by nature for secondary uses. If you go pulling healthy leaves during a flush, the plant will be pulling it's reserves from elsewhere. If you over-do the defol, it could shock the plant and delay the finish. No one can answer your question with 100% certainty, but lots of people do pull the leaves. Although, I'd keep searching the forums to see what others are doing and with picture evidence to backup their claims. I apologize if this isn't a good enough reply to your question.