Hello: Often the factory anode being removed gets deformed and needs to be replaced. The bolt trick is to prevent collapse of the pipe nipple. This prevents tearing the nipple and leaving a metal ring in the tank’s port. The ring can be tough to remove. Replacement anodes usually have a longer pipe nipple and are easier to grab with a wrench in addition to being stronger with more steel.
So, I’d plan on replacing the factory anode but if you do remove it without damage and if it’s magnesium with substantial metal left on it, go ahead and put it back in 😉