I don't think they are saying that you and I (application developers) should be writing assembly (they mention C/C++, and refer to C++ libraries elsewhere), unless we want to.
What they do emphasize is that the operating system was written in assembly, and while I don't know the members of the team personally, I'd guess anyone who has completed a project such as this (with this level of polish and utility) is at least potentially capable of being smarter than your average compiler.
I'd also like to state that I do agree, for a vast amount of software development, the convenience of higher-level languages and API's outweigh the associated performance disadvantages but for some programs, the ones that talk directly to hardware and who's library functions are called billions of times a second by application programs (and let's add, that are written far less frequently than application-level code) the assembly approach is justified.
Of course you're welcome to build something similar in a compiled language and prove us all wrong :)
What they do emphasize is that the operating system was written in assembly, and while I don't know the members of the team personally, I'd guess anyone who has completed a project such as this (with this level of polish and utility) is at least potentially capable of being smarter than your average compiler.
I'd also like to state that I do agree, for a vast amount of software development, the convenience of higher-level languages and API's outweigh the associated performance disadvantages but for some programs, the ones that talk directly to hardware and who's library functions are called billions of times a second by application programs (and let's add, that are written far less frequently than application-level code) the assembly approach is justified.
Of course you're welcome to build something similar in a compiled language and prove us all wrong :)