Let's at least compare apples to apples. Pun intended.
A side point: it was the patent clause of the GPL v3 that frightened them off. The GPL doesn’t require “upstreaming” of anything — you merely have to release the source code you used; any use of that code by another person is that person’s responsibility.
More generally on Apple: they just treat open / proprietary as another tactical tool. When they were on the ropes (e.g. late 90s) they happily embraced open standards like mp3 and jpeg, yet also happily purchased a license to .rtf. They quickly realized the ipod needed Windows support. Then as (and where) they became stronger they stoped caring.
In the case of collaborations between separate companies, secrecy becomes a problem because inevitably, details that are held close and not communicated turn into stumbling blocks. For a collaboration between Nvidia and Microsoft for instance, the teams at Microsoft involved with the project would need the same level of access to Nvidia's half as Nvidia's employees do in order to be as effective as Apple's internal teams have been. This isn't impossible of course, but historically Nvidia is not inclined to do things like this.
The question further is this model extended to say china. Many things happened in china was closed to outside. Not much as a secret but more like a big firm operate cheaply in a world economy. Would others compete or like apple others have to follow inline to get the supply. One wonder.
In addition, I think Nvidia's tendency toward extreme secrecy would quickly become an obstacle.