Open Domain is not a binding vow.

Open domain is not the result of binding vow, it is pure skill.

The second you unlock it, you **automatically** obtain the +200m range.

It's the same principle as heavenly restriction.

Toji did **not choose** to have phenomenal physical stats, that is simply the byproduct of being born with zero cursed energy. An automatic trade-off.

Kenjaku & Sukuna did **not choose** to have additional range, that is simply the byproduct of their domain having an escape round. An automatic trade-off.

**Simplest way to think about it:**

Domains are much bigger on the inside than they look on the outside. With open domain, the internal distorted dimensions (just like people) have no walls keeping them in, so they fan out; overlayed onto the real world. Is that easy to visualize?

The range is not a conscious action, it's automatic (a side effect).

Now for that one individual who can't read and is gonna come in saying "but it is a conscious choice, Sukuna changed his range to not hit X or against Y" ... I'm delegating the comments to deal with you.