I can guarantee you that the 16 Non-Stop Hits is the first one in the series of 5 - no idea why they changed the name of the series - but thinking about it, why would they start a series at Volume 2?
I've been through the entire Motown LP listings (i used to collect the albums) and there is no Vol1 listed elsewhere.
Latest Publishing date on 16 Non Stop Hits is 1971, so it's possible that it was an early 1972 release.