What is the meaning of `sourceRef`?

[Sleepful]

AFAIK it is meant to reference a GitRepository kind, one such example is in the docs:

kind: GitRepository
metadata:
  name: podinfo
  namespace: default

...

kind: Kustomization
metadata:
  name: podinfo
  namespace: default
spec:
  sourceRef:
    kind: GitRepository
    name: podinfo

so here the sourceRef.name is pointing to the GitRepository from above.

But I am confused by examples using sourceRef.name: flux-system:

  sourceRef:
    kind: GitRepository
    name: flux-system

Which GitRepository resource would this be pointing at?

I would expect it to point to a resource like the following, but it is not present in the examples:

kind: GitRepository
metadata:
  name: flux-system
  namespace: default

Edit: it seems that the flux-system repo is generated by bootstrap, and this is why it is not shown in the examples. Do you think I could add this to the docs?