Yes, if they are talking about Swift, they’d mean Metal for direct GPU programming. I have never read up about Metal, but I think it was Apple’s response to games developers moaning and complain that they could not control hardware directly, but Apple provided APIs to do so (with the code the games programmers would have written for themselves).
I can see two words badly used from C-think. First ‘metal’ where the word is bandied about to say “C is close to the metal”, meaningless and it really isn’t, and you don’t want to be anyway, except for very rare hardware-oriented programming, for which I propose very small languages doing what both C and assemblers do, but with the hardware semantics in the language and in the compiler rather than in defines or inline assembler. This is rather the Burroughs approach and still the best.
Secondly, what I have observed is misunderstanding of the word and concept of ‘abstraction’ , which they interpret to mean software layers, since Apple’s API approach is called an ‘abstraction layer’. This detracts from the real meaning of abstraction, which is just a way of thinking about things (what all of computing is about).
(Sorry for the rave… not really!)