To confirm the reason for the LUN OS type is purely about the offset. The offset ensures that the LUN and OS are matched regarding where blocks are written. If they do not align then we have misalignment which causes performance degregation, please see: What is an unaligned I/O?
For your WIndows 2012 servers you must use LUN OS type windows_2008.
Also, you are using an Release Candidate (RC) release of an old ONTAP version that went out of Engineering Support on 30-Aug-15. If possible you should be looking to upgrade to the Supported Data ONTAP 8.2.5.
However, your issue is that the second server cannot see changes to the LUN. I am assuming this is not a Windows Cluster enviornment. In which case only one server can connect to the LUN at a time otherwise you risk data corruption. If you are only connecting to the LUN via Server A, then this is not a problem and rather is your issue that at a file system level Server B cannot see the changes?
Can you clarify how Server B is attempting to view the files; is it via connecting to the LUN on the storage an mounting it as a drive in disk manager, or connecting to a share hosting on Server A?