You are talking about machine code, that is basically never programmed in anymore, instead we use assembly that has a way more intuitive mnemonic representation that accurately represent it.
Programming languages are higher level abstractions that can also be translated into machine code, but are not accurate instruction by instruction representations of it like assembly is.

The clear advantage of higher level languages is that they can be used disregarding of what processor the code is running on. And that higher level languages are more intuitive and structured, with many features to make the programming faster and easier.

My guess is that even for an AI, it would still be easier to use a high level language, as there is way more material to learn from, and the same amount of programming can be done in way fewer steps.
Back in the 80's and 90's I loved programming in Assembly language, and everyone who claims compilers are just as good don't know what they are talking about. I could often make assembly code that was about 20-100 times faster than C (M68000 Assembly), which is generally known for being a very high speed high level language. Things that were claimed to make no difference to make in assembly like i80387 math, I could accelerate to 2-5 times the speed. The argument was that i80387 math was simply too confusing and hard to learn to be worth it, which is bullshit. It was just hard to get good instruction books. When you had that, it was no harder than Assembly in general.

But even for an AI, using assembly or going directly to machine code, would mean extra work for the AI. And it increases the risk of bugs. You have to be very careful when programming assembly. And I don't think an AI understands that well enough to actually work.

It would be nearly impossible to debug. Kinda useless.

Also kinda impossible to get anything done that is bigger than the context window.