An indie band can still have a record label backing them, but calling themselves that sets an expectation that their music will likely be outside of mainstream appeal. The same goes for indie films which can still have massive budgets and distribution channels thanks to major studio backing. They just tell stories that won’t follow the formulaic mold that big picture releases are beholden to.

You kind of have to disconnect the word “indie” from meaning “independent.” The industry has matured enough that indie refers more to an overall aesthetic and expectation for consumers rather than a fully independent game dev. Publishers are ultimately acknowledging the legitimacy of indie games as a part of the market and dipping their hands in them. I’d still expect the studios to retain most of the creative and design control, but they’ll have access to the marketing, analysis, and distribution relationships that publishers can provide.