their investment in teaching you their IP -- that's the theory

you trade getting to learn for agreeing not to use it against them for a while -- is the theory

at line worker level i'd argue this is nonsense, at 'how to mill iPhones from a single block of metal' or 'self driving car brain' maybe its real, but there are ndas and patents for that

Yeah, that theory's a load. If the fear is formal IP theft then as you point out there are harder protections for that. If the fear is they'll learn your business practices and use them to compete with you, then you suck and they deserve to win. Because you're the established business with all the advantages and existing customers, even if they have the capital lying around to start a copy-cat business tomorrow you should be able to wipe the floor with them and make sure they never get off the ground.

> their investment in teaching you their IP -- that's the theory

In your example, they cannot claim the skills and basic education that gets you up to the point of "how they mill iphones within a context" (i.e. the milling, operating the machinery, physical properties of the metal, etc)

They are not legally able to include a huge educational backbone of knowledge (that they may have taught you) as their prioptary IP. Again, NCs don't prevent that disemination. That disemination can happen without employment.

context on the milling skills:

https://beneinstein.medium.com/no-you-cant-manufacture-that-...

I really get a kick out of this thinking, because there's literally no alternative from the employer's point of view. If you want to hire someone to do a job, you have to teach them how to do the job.

To impose punitive measures after-the-fact because someone taught you how to do a job that they needed you to do seems hilarious even on the face of it.

To be clear, saying "You're not allowed to use our IP or our machinery or our supplies" is totally reasonable; if I quit Starbucks, then of course I won't have Starbucks machines or merch. To say that you're not allowed to do something because they happened to be the ones to train you seems just silly.

I get very strong middle-school vibes, where you introduce your friend-from-another-school to your group, then get mad when they become better friends with someone else than they are with you.