Can Flowlity stop out-of-range products from being ordered?

Yes, that is the core of the feature. Products that are not active in a store's assortment are excluded from that store's order proposals, so buyers stop seeing and correcting lines that should never have appeared.

When a product is intentionally outside the standard matrix, you switch it on for the sites you choose as an exception, and every override is kept in a dedicated exceptions tab you can review.

Because assortment and replenishment share one engine, the assortment rule stays attached to the order, so a planner can see whether a reference is missing because it is out of range rather than because of a buffer or a supplier issue.