Samsung Display is looking to expand its ultra-thin glass business by offering the technology to companies other than Samsung Electronics. Some of the first new customers include Google with its upcoming foldable Pixel smartphone and possibly even Apple when it launches its own foldable in a few years.
https://www.notebookcheck.net/Google-expected-to-release-its-first-folding-phone-in-collaboration-with-Samsung-Display.542532.0.html
...and since Samsung has been providing phone & tablet displays for Apple devices for a decade, it makes sense for the Cupertino tech giant to consider foldable devices.