The exhausting part usually isn't any single task (the permission slip, the dentist appointment, the fact you're out of the good snacks) — it's carrying all of them in your head at the same time, plus the ones that haven't happened yet but you're already tracking. That's the "mental load", and no to-do list fixes the underlying job of running a household, but a decent one can at least stop it living entirely in your memory.
The brain dump button is there for exactly this: the permission slip, the appointment, the snack list, the thing you keep meaning to book — all of it goes straight into Someday in one go, out of your head and somewhere you'll actually see it again. Today then holds five tasks, on purpose, because a day with a household's worth of logistics in it doesn't need a to-do list adding twenty more items to feel behind on. Someday keeps the rest without demanding a decision right now. Just try it on the next chaotic morning — dump it all, then pick five you can actually finish.