> I can understand someone not having an inner voice, but I can’t see how writing is possible without inner speech. Otherwise, how can you have thoughts prior to writing them down?

The conscious experience of inner voice/speece/eye/nose/whatever is not really saying something about how the rest of the brain functions. Almost everything anyone does is indeed not projected in inner mind before being executed. The subjective experience is a post-hoc narrative of what the mind did, not really a part of the planning process itself. Think about running in a dense forest for example. There's no way to plan with inner mind where to direct your eye muscles first and then having received the visual input, plan with inner mind where to put your feet on the ground to not trip on a rock or root.