Demand doesn't matter right now. Tesla Q1 sales is mostly dependent on how many chips they can acquire. So the actual number is very hard to guess.
Demand matters greatly even when delivery volume is fixed (
Inelastic supply).
Different vehicle models, versions and configurations vary widely in the gross profit Tesla can get with the available components supply. In the extreme, a Model S Plaid with $12k FSD and all the $1-3k extras for wheels/paint/interior probably earns an order of magnitude more profit than the cheapest Model 3 SR. A growing backlog for all vehicles increases Tesla's power to allocate production as they see fit.
Demand also affects the price Tesla can charge for a given car configuration, because they're effectively auctioning off the cars in a global bidding war. Tesla has been generous in allowing the order backlog to get so long, because this whole time they could've simply raised prices even more to reach a supply-demand equilibrium. (Thought experiment: Raise Model Y price to $90k and see if there's still a backlog). Tesla is a benevolent monopoly.
Currently, FSD and Performance orders are being prioritized and prices for all models have risen an average of 7% since last year. Extremely bullish, all thanks to high demand (edit: and Tesla's competitive dominance).
Additionally, Tesla's fat gross profit margins let them bid more for chip supply, other components, and expedited shipping. Elon said on the earnings call that many suppliers worked nights and weekends to make 2021 happen how it did. Overtime surely was compensated by Tesla somehow, and demand paid for it.
Longer term, this demand still matters because Tesla's investors and suppliers see this position of strength and increase their willingness to risk funding a more aggressive rate of expansion. Those nickel mining firms, chipmakers, aluminum smelters and battery manufacturers see the overwhelming demand and it gives them more confidence to go hard, thus accelerating the sustainable energy transition.