Not firmware sure, but if one boots the Pi from the software that's just as bare metal as anything else. And the age of the GCC version is completely irrelevant to whether something is bare metal.
I didn't say that GCC version is relevant to bare metal definition, I said it's 15 years old. And when you try to draw conclusions, and derive strong opinion, based on the codegen output but you're using 15 year old toolchain, and btw pretty shitty CPU core, something isn't quite right. This article is just a good display of never ending cargo-cult programming myths.
Their stuff isn't running on top of Linux on the Pi.