They came uninitialized, but yeah it could be worthwhile to actually zero and fully format them. They are decently fast at 275 MB/s but even that's 16 hours to do one pass. Maybe let it run over the weekend
16 hours isn't that bad. I recently had to zero my old 2tb Time Capsule and just let it run overnight and during work, wasn't so bad. You'd also get to detect bad sectors, figure out how good the drive is in terms of what % of the drive is actually usable for large sequential writes
