Getty used to refer to the content they owned outright as wholly owned. The advantage of such content is that you can offer introductory freebies (for example) easily because you have no one to pay a royalty to.
Looking at the Shutterstock portfolio for Lightfield Productions (skimming it; it's huge) it's not filling gaps in the collection. It's a collection of every stock stereotype and cliche; people heavy; generic scenery (autumn, mountains, summer) but no specific cities, etc. All very professionally done, well lit, "diverse" models.
When you consider the terrible stunts DepositPhotos has tried in the past (
Shotshop as but one example), this type of collection allows them to do that sort of deal without ticking off contributors.