“In 1993, a Linux engineer found a nonintuitive case with load averages, and with a three-line patch changed them forever from “CPU load averages” to what one might call “system load averages.” His change included tasks in the uninterruptible state, so that load averages reflected demand for disk resources and not just CPUs. ”
A great bit of research explaining not just what “load average” means in general, but how and why Linux load averages are computed differently from other *nix systems.
http://www.brendangregg.com/blog/2017-08-08/linux-load-averages.html