do they make you sort your boards ? what happens if you had a couple pounds of low grade in your high grade? do they scar your whole load. im still learning how to sortand dont want to lose money by accident

The principal idea for boardsort it to send in sorted loads.
One single board isn't going to kill you but not sorting motherboards will get the lowest class. And tossing a bunch of peripheral in your telco will get you all peripheral
Will a single low grade board kill telco? Probably not. But sending a big crate of mixed boards won't win you any fans and won't get you any chance of higher grades