Hi,   I can try create a case up and check that, but it wont be that immediate to get a response from them. I tried getting more information about T640 why it isn't supporting SGX, it's probably due to the support of processors that have SGX capability. From this documentation, E-2100 have SGX feature, but T640 does not support the processor.    I'll check why iDRAC have that particular settings that you have screen captured. If you don't mind, send me a PM of your server's service tag.
BIOS version 2.11.2   iDRAC version 5.0. Intel SGX not showing in BIOS. Change SGX Launch Control Policy  to Intel Locked in iDRAC Bios settings shows NIC016: AttributeValue cannot be changed for disabled AttributeName SgxLcp. No response action is required. Any solutions?
T640 cant enable Intel SGX (Software Guard Extensions)