When using the E-tile Hard IP for Ethernet Intel® FPGA IP in "single 100GE with optional RSFEC" mode, why enable RSFEC option is greyed out?

Due to a problem with Intel® Quartus® Prime software version 18.0 and earlier, the enable RSFEC option is greyed out in E-tile Hard IP for Ethernet Intel® FPGA IP in single 100GE with optional RSFEC mode.

To work around this problem in Intel® Quartus® Prime software version 18.0 and earlier, it is suggested to use "100GE or 1 to 4 10GE/25GE with optional RSFEC and 1588 PTP" core variant in E-tile Hard IP for Ethernet Intel® FPGA IP.

This problem has been fixed starting in version 18.1 of the Intel® Quartus® Prime software.