Why does nouz ask for access to all orders?

Because Shopify's normal order permission only reaches the last 60 days. A permission is what Shopify lets an app see. The extra one, called read_all_orders, lets nouz read your whole history. That is what the first sync brings in: every order since your first sale.

Sixty days are not enough for a real profit picture. They cannot show last year's busy season. They cannot show a product's true return rate, because returns come in over months. And they cannot tell you whether this month is better than the same month last year.

The Forecast needs it too. It builds the months ahead from the same weekdays a year earlier. Without a year of orders, it could only repeat your last four weeks.

The permission is read-only, like every permission nouz asks for. It lets nouz read your history once, then keep it up to date with each sync. It gives no way to change an order or anything else in your store. Shopify shows it on its own approval screen when you install nouz.

You can check what nouz got. Open Settings, then Integrations, and click the Shopify row. Look at the first line under What nouz can read. If it ends with your full history, all is well. If it ends with from the last 60 days, Shopify gave only the normal permission, and older orders are missing from your P&L. Order history also shows the first day nouz has.