chore: document init parameters

[gtm-nayan]

closes #7200

The internal types aren't exposed as a public API and shouldn't be relied on but figured it'd be nice to document these anyway just so no one forgets what these are when we context switch to the next major

A few left to do still as I couldn't quite describe them, feel free to make suggestions as review comments or push

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[benmccann]

it'd be nice to document these anyway just so no one forgets what these are when we context switch to the next major

will we need to remember what they are once we stop working on this codebase?