What's the difference between '...' and the more common 'pass'?

In this case, functionally, nothing. Some other commenters have suggested it does something interesting by implying "AI will provide the logic," whereas "pass" doesn't necessarily do that.

In code, using ... implies that the code is yet to be written. pass means it's explicitly a noop.

I find students correctly infer what to do with "..." whereas they were afraid to touch "pass".

E.g, if I gave them this:

    def foo(x):
      ...  #add your implementation here
    
    def bar(x):
      pass #add your implementation here

I'd get back this:

    def foo(x):
      return x+1
      
    def bar(x):
      return x+1
      pass