It is possible to get more reliability by using hard drives that come from different batches and ideally manufacturers. Otherwise they may fail too close in time. The excellent answer of @Eliodorus explains this enough.
Of course, it does not matter who shuffles the drives. If your provider confirms it does that for you already, no need to care about. If not, thenHowever it seems not reasonable to do some forensic on maybe even different provider and conclude somebody does for you needif you are not told directly. Providers usually are not lazy to doadvertise various measures they take to increase reliability of they drives.