On the project page it states:

For editors to see the Save as Draft checkbox you need to either grant "administer nodes" permission, or you can use Override Node Options and grant "override [nodetype] published option" for the node types that you want the editor to save drafts for.

However after not seeing the "Save as Draft" checkbox and looking in the code I found that editors do need perm "access save as draft" while "administer nodes" is not used at all. This is in contrast to the detailed message shown above node revisions that require either "administer nodes", "override ' . $node->type . ' published option" or "revert revisions".

To summarize, setting a revision to be a draft requires "access save as draft" while changing revisions requires "administer nodes", "override ' . $node->type . ' published option" or "revert revisions". I propose changing the quoted text to:

For editors to see the Save as Draft checkbox they require the "access save as draft" permissions. For editors to enable a draft revision they require the "administer nodes" permission, or you can use Override Node Options and grant "override [nodetype] published option" for the node types enabled.