The documentation sections for "Node scaling for etcd" (release note [1], recommended practices [2] might be confusing. 

    always

    1. Read the section within the context of OCP docs where, usually,
       the term "node" refers to any OCP cluster node and
       the term "cluster" refers to the OCP cluster.
    

    The sentence

    "you can scale a cluster to up to 5 nodes as a post-installation task"

    implies that an OCP cluster can have a total of up to 5 nodes.

    The documentation makes it clear that it is talking about the
    control plane (nodes) and the etcd cluster (if it is necessary to
    talk about the etcd cluster at the level of abstraction of the
    documentation sections).

    It might be enough to insert "control plane" in the current text
    as follows:

In this release, if your cluster is installed on a bare metal platform, 
you can scale a cluster control plane to up to 5 nodes as
a post-installation task. The etcd Operator scales accordingly to account for the additional control plane node(s). For more information, see Node scaling for etcd.

    Disclaimer: I'm not a native speaker and I wouldn't call myself
    an OCP expert. :-)