A concern has been raised in the OpenCMIS TCK about whether a PWC can have cmis:isLatestVersion=true.

https://issues.apache.org/jira/browse/CMIS-431

The difference of interpretation is whether or not a PWC has any characteristic of a version.
For me, a PWC is not a version and (consequently) can never be considered the latest version.
Florian has a different interpretation.

This is not clear because the spec sometimes talks about "version" in a loose sense and says that the PWC is a kind of version. And also it sometimes hints at the fact that the PWC is part of the version series.