Another potential purpose for such a leak would be to boost the stock price.
Apple may be prototyping a dozen screens at a time, but they'll let someone else build the factory to produce millions a year.
> The screens are far more difficult to produce than OLED displays, and the company almost killed the project a year or so ago [...] consumers will probably have to wait a few years before seeing the results.
So the best-case scenario is that Apple finishes developing this technology in a few years, and the worst-case scenario is that they kill this development, which almost happened already.
This could go either way both for Apple and for screen manufacturers. It only makes sense to explore an option without all this uncertainty, by seeking a new middle ground.
Seems indeed very little interest for Apple. I'm sure any effect of a public leak can be as efficiently done with regular phone call. By shear size, Apple is very close to all its providers, the "pride and prejudice" drama is creative license of the media to animate what is mostly regular boring corporate interactions.