No, it's not. What a silly thing to say.
Is the developer writing Metal code? No. Then they're not using it directly. They're using an abstraction.
"using it directly" means the developer is writing Metal code themselves. Writing Unity code that eventually gets compiled to Metal is not writing Metal any more than writing C that gets compiled into machine code means you're writing machine code.
Think of it this way...if someone wants to hire an experienced Metal developer for a Mac-exclusive game, do you think someone who's only developed using a game engine like Unity would be qualified?
> You forgot the Playstation (LibGNM/LibGNMX) and Nintendo ones (depending on the generation, microcoded GPU, GX (Wii), GX2 (WiiU), NVN (the main one on the Switch), Vulkan and GL 4.6).
Irrelevant to the conversation. We can talk about developing with proprietary APIs and continue to just use Apple's Metal as an example without bringing up all the other proprietary APIs. Not sure why you think I "forgot" all the other APIs.
You forgot the Playstation (LibGNM/LibGNMX) and Nintendo ones (depending on the generation, microcoded GPU, GX (Wii), GX2 (WiiU), NVN (the main one on the Switch), Vulkan and GL 4.6).