In fact the RAID volume will be initialized until you boot into the operating system once it is already installed.
In the other hand, this volume will not be marked as bootable, and it cannot be used to install an operating system on it since Intel(R) Rapid Storage Technology cannot use volumes larger than 2 TB as bootable units. You can use larger drives only for data storage.
In this case you will need to create a smaller RAID volume and use the rest of space to create another one, or install the operating system in a separate bootable hard drive.
Thank you. This is 100% Correct!
I also encountered the problem you described regarding the 2tb limit. Ran down to buy a 500gb disk for system.