A Storage Spaces Direct (S2D) cluster with nested resiliency requires exactly two server nodes and is supported on Windows Server 2019 or later, and Azure Stack HCI, version 22H2 or later.
This configuration allows for the management of two data copies (or "nested") within the two nodes for data redundancy, but you cannot add a third node to such a cluster.
Nested resiliency is a capability of Storage Spaces Direct in Azure Local and Windows Server. It enables a two-server cluster to withstand multiple hardware failures at the same time without loss of storage availability, so users, apps, and virtual machines continue to run without disruption.
Reference:
https://learn.microsoft.com/en-us/windows-server/storage/storage-spaces/nested-resiliency