A configurator rule is a constraint the manufacturer writes once: this roof pitch needs that truss, this width cannot take that door, this option requires the upgraded frame. The rule blocks the invalid pick at the moment it is made, in the dealer's session, so the person who would have made the error never gets to make it and the shop never sees it.
That is the whole mechanism, and it is worth being precise about, because this is the claim the category usually inflates. The figures that circulate on this subject come with no source attached, so none of them appears on this page, and we will not put a percentage on your error rate from here. The quoting numbers that do survive a source check live in our custom product quoting statistics. What a rule system changes is structural: a class of mistakes that used to be caught late, at the shop, at delivery, or by the customer, is now caught at the earliest possible moment, by software, at the click.
Late errors are the expensive ones. A wrong spec that reaches the shop becomes scrap, rework, a delayed delivery, and a dealer arguing about whose fault it was. A wrong spec that never leaves the configurator costs one red outline and a second click.