I don't get why they struggle so hard making the dungeon resettable without depleting the keystone. What does it change? You still will only get one loot crate per keystone. And if you want to recharge your keystone you can do so also right now.
If you are in such a dedicated group that you want to make the timer, you will just complete the current run and then repeat it with the depleted stone until you make it.
I don't see why it would be so hard to not have to complete it first and then start again (where in pugs you will very likely find no other players to join) but to be able to reset it midway and still get loot.