I mean in that sort of case then the group would defer to the person more knowledgeable in that specialty, same as what happens when after brainstorming people split into small groups or volunteer for individual responsibilities. Crowdsourced decision making is meant to be for the bigger aspects, stuff like what the end goal of a project should be. Smaller, extremely specialized aspects should get handled by those best equipped for it, that’s not a hierarchy. Listening to an expert is just respecting someone’s knowledge, and as long as they don’t have actual authority over you, then there’s much less risk of corruption taking place. There’s a quote from I think Proudhon Bakunin that I can’t remember off the top of my head, I’ll come back and edit this when I find it. But effectively, it boils down to the difference between authority as in power over people, and authority as in knowledge.

And people who help organize and manage jobs also don’t necessarily need to be part of a hierarchy either. If the group agrees that someone is extremely effective at helping resolve conflicts or suggesting the best path to take and that sort of role is desirable for the project then that’s what they should do. The difference is that they aren’t in a position of power over anyone. They don’t have the unilateral ability to fire someone (nor does any individual), or take away their income/ability to live. And since they don’t have that power, they aren’t in a hierarchical position over anyone. If they start trying to force their way without taking feedback then the group will stop listening to them and appoint someone else if they still feel that it’d be useful. Without a position of authority over people no hierarchy exists in the definition used in anarchist theory.

Edit: Thanks @onoira@lemmy.dbzer0.com! Knew I read it somewhere on here recently.

Does it follow that I reject all authority? Far from me such a thought. In the matter of boots, I refer to the authority of the bootmaker; concerning houses, canals, or railroads, I consult that of the architect or engineer. For such or such special knowledge I apply to such or such a savant. But I allow neither the bootmaker nor the architect nor the savant to impose his authority upon me. I listen to them freely and with all the respect merited by their intelligence, their character, their knowledge, reserving always my incontestable right of criticism censure. I do not content myself with consulting authority in any special branch; I consult several; I compare their opinions, and choose that which seems to me the soundest. But I recognize no infallible authority, even in special questions; consequently, whatever respect I may have for the honesty and the sincerity of such or such an individual, I have no absolute faith in any person. Such a faith would be fatal to my reason, to my liberty, and even to the success of my undertakings; it would immediately transform me into a stupid slave, an instrument of the will and interests of others.

— Mikhail Bakunin, God and the state, Chapter 2

But yeah, respecting peoples expertise in topics, splitting up work, or appointing people to give managerial suggestions aren’t hierarchical. A lack of hierarchy is not a lack of structure, it’s just a lack of power and violence being used to oppress or control people. Efficient structures like these tend to naturally fall out of self-organization once the monopolies on violence used to prop up hierarchies are removed.