Correct, thus... monorepos.
Now, for Linux, the kernel<->user-land ABI is deemed stable, so you don't have to coordinate updates with the C (and other) run-times.
Other OSes did have the kernel and the C library in the same repository, so those have had the privilege of making their kernel<->user-land ABIs private. E.g., Solaris/Illumos, OS X.
Now, obviously if you have a monorepo for your startup, you might not include the Linux kernel in it mainly because you probably don't want your devs changing the kernel unless that's integral to the startup's purpose.
