CAA mkcluster fails if repository disk is Clariion/Invista

Regarding IBM doco - IBM IV53226: CAA MKCLUSTER FAILS IF REPOSITORY DISK IS EMC CLARIION/INVISTA - United States

IBM have a local fix (not listed in the article) but have provided us with - ftp://testcase.software.ibm.com/fromibm/aix/IV53226s1a.131211.epkg.Z

I'm looking for a more elaborate explanation on this issue from a storage perspective. It claims the mkcluster command on AIX will fail when a hdiskpower is chosen as the repository disk and the underlying SAN is EMC Clariion or Invista.

What is it in particular to the Clariion? Why does this error occur only when using the LUN served by Clariion via PowerPath as a repository disk? I'm not an AIX person so what is the local fix actually fixing?