The Crimson Binome
Hero
If you have 1 hit point, then you're not in the process of dying. You could wait around for three years, and having 1 hit point will never kill you (assuming you took care of outside factors, like food and water). The spell can go ahead and set you to 1 hit point, and that's a stable place for the magic to stop.So? What does that have to do with anything? Being at zero hit points could mean you have anywhere from almost zero seconds to live (ie - it's just before your turn and you already have 2 strikes and you're about to fail the third) to almost zero seconds before you get back up again (it's just before your turn on 2 strikes and you roll a 20) to 1d4 hours before you stand up (you were on 2 strikes and 2 successes and you roll a success). Being on 1 hit point is even more variable.
When you're at Exhaustion 5, you are in the process of dying from exhaustion. No matter where it sets you along that final day, it's still only a matter of time before you hit Exhaustion 6. Whether that is minutes away, or hours away, we have no way of knowing. There's no stable place for the magic to stop working. Why would it set you back to exactly the start of Exhaustion 5, when that point is exactly as unstable as any other? Why wouldn't it set you six seconds away from Exhaustion 6? There's no equivalent "Exhaustion 5 and stable" like there is "1 hit point and stable" or "zero hit points and stable".