I believe I have done this before without a hitch. Other sources seem point to adding ISCSI LVM as well however, I am not able to add an LVM its asking me to select a Base Volume. What step did I forget to do?
You need first to add the iscsi storage ( unchecking the box use Lun directly)
After that when doing "add LVM", you use this iscsi storage as the base storage ( the iscsi storage should available in the drop down list)