So, totally ancedotal evidence, but: I got an open box Asrock Rack server board a while back...came with EVERYTHING the retail one came with, even cables and IO shield still sealed in the bags. OTOH, they only guarantee you'll get a bare board.
Maybe...just maybe...if its a server board, you have less chance that some aspiring young gamer trashed it by accident and returned it.
They used to have a "no warranty" policy ( other than any manufacturers warranty for items that hadn't been registered by the original purchaser). But, they also had a "no questions asked" return policy within 30 days, in case the board was DOA.