I think if the NSA want in they don't need to bother with stuff like this, and if Apple were forced to compel they wouldn't be documenting anything related to it
If we're spitballing tinfoil type stuff, I'd guess it's in the NSA's interest to have American OS's like MacOS be as secure as possible. I'm sure they have access to any of Apple's certificate chains, cloud data, and could decrypt a Macbook as well as Apple could, but I don't see known software backdoors being desirable.
you would think that a sane national security strategy is to maximize security of every citizen, but somehow nsa prefers to undermine everyone else's security to have a chance to hack anyone and everyone
That indeed makes sense, but sometimes one hand doesn't know what the other does. Also not all decisions are rational (actually it's the other way around). A better example for this is the FBI tho, since they really hate any security mechanism that plebs can use.
I'm not saying that the NSA has any involvement in this situation, but clearly their strategy is sometimes to undermine security. It's not their whole schtick, because of NOBUS, but still part of it.
That and they've always been fairly strongly linked in the past anyway - the kind of sexy counter-intelligence has always greatly benefitted from a good offense.
Edit: It seems downvoters know something about the patriot act that I don't, because last time I checked it still forced US companies to comply with requests from US secret services. If you know more please explain rather than downvote.