Datapoint's drives were Shugart ... so, if Memorex preceded Shugart on the market, a Memorex OEM may have preceded Datapoint. I only know that Datapoint was the first commercially-available customer for the Shugart drives.
Datapoint systems with 8" floppy disks DID use "IBM-labelled" diskettes. IBM invented the floppy disk, but Datapoint was the first commercially-available computer system to offer them. The IBM label (on the jacket) was common ... as long as the diskettes were 'soft-sectored' -- as most were --...