What is Apple protecting that won't eventually be open anyway?
They're protecting the value of NDAs and contracts people sign with them.
Almost all companies, of just about every size, have information they don't want being publicly available. Sometimes it's pointless, sometimes it's materially harmful or catastrophic to the company. Apple, for various reasons--legitimate or not--has a habit of being secretive about a lot of things.
But the bottom line is, they have contracts and NDAs with a lot of companies and people. Sometimes the NDA covers a piece of prerelease hardware or software that's already been announced and will be publicly available in the near future. Other times it's buying a smaller company, details of a product design, CPU design, or upcoming software the disclosure of which would be somewhat or extremely harmful to the company.
Violating some NDAs will cost Apple nothing. Violating others could easily cost them hundreds of millions of dollars.
But if they allow people to blatantly violate their NDAs and don't react at all, it sets a terrible precedent. "Violate an agreement with us, and nothing will happen to you."
I would challenge you to find any company of even moderate size that had an entity sign an NDA or other contract with them, then after having it quite publicly violated isn't going to at least void the rest of their contracts with that entity.
It's a very, very simple section of the contract; excerpting relevant bits:
9.1 Information Deemed Apple Confidential
You agree that all pre-release versions of the Apple Software and Apple Services (including pre-release Documentation), pre-release versions of Apple hardware [...] will be deemed “Apple Confidential Information” [...]
9.2 Obligations Regarding Apple Confidential Information
[...] You agree to use Apple Confidential Information solely for the purpose of exercising Your rights and performing Your obligations under this Agreement and agree not to use Apple Confidential Information for any other purpose, for Your own or any third party’s benefit, without Apple's prior written consent. You further agree not to disclose or disseminate Apple Confidential Information to anyone other than [basically, your employees] [...]
11.2 Termination
This Agreement and all rights and licenses granted by Apple hereunder and any services provided hereunder will terminate, effective immediately upon notice from Apple:
[...]
(b) if You or any of Your Authorized Developers fail to comply with the terms of Section 9 (Confidentiality)...
It's that simple. The contract specifically calls out violation of the confidentiality clause as one of five things that will get your contract immediately voided. It would be downright strange if Apple
didn't void the contract for highly public violation of this clause.
It says "don't disclose information about pre-release versions of Apple hardware, or we will immediately terminate your contract." This is exactly what Apple did. The contract also includes the ability to sue someone who discloses confidential information for damages, which it looks unlikely Apple will do.
In fact, if you read carefully,
iFixIt was the one that terminated the contract. The termination just didn't become effective until Apple notified them.