The benefit of not relying at all on android code? Well, that would be not having to constantly adjust to what happens in the android code base. If google introduce proprietary code that the os depend on, one would have to create substitutions for that.

But with PinePhone and running e.g. postmarketos, then it's more pure linux and not have to relate to android and google's whims.

But I must say I AM happy with /e/os as a free degoogled android os. But it will still never be as good (or better) than "the real thing". At least that is my main concern