I wouldn't like any of my fan leaves to drop off! Even during flowering although it dose happen and not a big deal if it is only one or two of the bottom ones.
I suppose growers will argue as to wether to leave them or pull them, personally i leave them till there completly dead, as long as the vascular system is still going the leaf is producing and of no burden to the plant, also if you let them drop the plant can heal itself better as there is no open wound for virus or bacteria to vector.
One thing i notice in flowering is all the new formed bud leaves have a very big surface area which kinda puts my few fan leaves to shame, i see that even if i loose a few fan leaves it is no great deal on the total surface area of the total leaves at that time. I would be worried if i lost a lot of fan leaves or they kept on dropping, would make me think i wasnt giving enough ferts maybe.
Yer you are a grouchy old d!ckhead whatchhowidoit but obviously know how to grow and helped me out a lot in the past thanks!lol! Peace