I'm not sure I can argue it any better than I already have. It's a question of whether or not the DM should have the flexibility to decide when and how exhaustion is reduced or increased. The toggle would allow DMs who don't want the script making the decision for them to have it turned off allowing them the flexibility to make the decision rather than having the script do it. The jungles of Chult are not the only situation where this comes into play. What if the characters are under a curse? What if they are on a plane of existence where they can take a long rest to regain spell slots and other resources but remain exhausted? What if the DM has created a world where you need a specific plant, or a specific location or something else before you can reduce exhaustion levels? A script that is otherwise very useful can therefore create a problem because it makes a decision for the DM that the DM doesn't want decided for him/her and thereby reduces opportunities for creativity and role-play. But, perhaps the better argument is: the script, as written, breaks the rules of D&D 5e because nowhere do the rules say that exhaustion is automatically reduced in all circumstances by taking a long rest. In fact, the rules specifically state: "Finishing a long rest reduces a creature's exhaustion level by l, provided that the creature has also ingested some food and drink ." (Emphasis mine, quoted from PHB p. 291). I cannot find any location in either the PHB or the DMG where it says that exhaustion level is ALWAYS reduced by 1 by a long rest - it's always conditional on getting food and drink as well as "rest" (since elves don't need to sleep, they still benefit from long rests by meditating, not sleeping, but they still need food&drink). And, under that circumstance, perhaps you shouldn't adjust exhaustion level at all since there's no way the script can know if the characters ingested some food and drink. So, if the DM isn't bothering with food&drink rules, then he can leave the switch toggled ON, but if he is bothering with the food/drink rules, then he can turn the switch OFF and make the decision at each long rest as to whether or not the characters satisfied the requirements to reduce exhaustion and adjust it manually.