Currently, this section is talking about

• CodeReady Workspaces server: 1 GB to store logs and initial workspace stacks.
• Keycloak: 2 PVCs, 1 GB each to store logs and Keycloak data.
• PostgreSQL: 1 GB PVC to store database.

But this is not true for (at least default installation) Codeready Workspaces.
As for storage requirements, Codeready Workspaces is using only one PVC - for postgres database pod.

This is probably just copy-paste error from upstream doc, where the 4 PVC's are true for default multi-user deployment/installation