"What needs to be "approved" by Apple."
on 10.12, the nvidia drivers were signed, but they did not have approval. The drivers did certain things apple didn't like so they were denied library validation. Things like little snitch/etc would break. This is because apple would reject window access in applications using library validation to the unapproved nvidia drivers, signed or not.
in 10.13 nvidia rewrote the drivers, changing how driver worked to appease apple overlords and in return apple blessed them with approval to be treated as trusted kexts that are allowed library validation.
Lets be clear on this. This REQUIRED Apple's blessing. Once the drivers adhere to certain rules, macOS goes "ok, i blesseth thee"
So can nvidia just say "screw apple, we'll release drivers anyways." ? Sure, but you can be assured these drivers would not be blessed by apple and would not work properly for the INCREASING number of apps that use library validation. Just because hackintosh users can have
https://github.com/acidanthera/WhateverGreen or nvidialibvalfix magically fix the problem doesn't change the fact that nvidia has a target audience that also includes a lot of mac pro users and even old imacs and macbook pros that still prefer the web driver over stock (web driver has MUCH higher opengl performance, metal performance about the same, but web driver is up to 30% faster still at opengl games).
Whatever pissing war is going on between apple and nvidia, i suspect nvidia is trying not to burn the bridges completely down just yet, because they do want apples approval to remain on their drivers so they can be used properly with SIP enabled and without hackery requirements if they aren't blessed.
I feel nvidia's approach of calling apple out is so they can encourage us as users to write to apple and show them that a relationship with nvdia still matters. That is what people should be doing at this point.
All this nonsense and conspiracy theories that nvidia is struggling with driver because of metal 2 and other stuff is just plain nonsense. I've talked with developers who have been working on metal for years now. Metal 2 is not a reinvention of wheel. it's literally just new feature extensions added to existing api that would not take that much effort to add. At most, the hardest part would be trying to get apple to approve certain nvidia gpus as Family2V1 feature set so every nvidia gpu didn't get locked into family1V4 and be locked out of using new metal features (hey there is that word again, APPROVE).
TL/DR. Nvidia has been good to us for years, I don't believe for one minute that they suddenly decided to drag their feet on purpose and make up stories because their engineers suddenly got stupid and couldn't figure out how to add 3 measly new api functions to their already existing and complex metal code. I bet drivers been done for at least 2 weeks if you want my honest opinion. This has apple written all over it.