I wouldn't consider seL4 to be a "C project". Yes, their github repository is mostly C, but the process of writing seL4 was extremely involved: write the kernel

I wouldn't consider seL4 to be a "C project". Yes, their github repository is mostly C, but the process of writing seL4 was extremely involved: write the kernel in Haskell, then write it again in C, then prove that the C is equivalent to the Haskell. seL4 is ~9000 lines of C, ~600 lines of asm, and ~200,000 lines of Isabelle (theorem prover). I don't disagree with your use of OpenSSH as an example.