I have been doing some testing with the latest build and have found the following issue.
When you extend an iscsi volume the client cannot view the additional disk space unless the iscsi volume is first removed from the target and then added back to the target.
I know, this should be improved (no set date) to send or force it to re-read the lv size. But for right now, the process is either from the Target end or logoff the MS Initiator then use diskpart.