While I understand that without the proper context (knowing a bit about bitstream protection in the Xilinx 7-Series FPGAs) my comment may seem a bit obscure, I

While I understand that without the proper context (knowing a bit about bitstream protection in the Xilinx 7-Series FPGAs) my comment may seem a bit obscure, I did read the paper. As the sibling comment mentions, the attack requires programming a plaintext bitstream in order to perform the readout of the WBSTAR register after the automatic reset caused by the HMAC authentication failure. Blowing the CFG_AES_Only eFUSE prevents the loading of that plaintext readout bitstream and the first stage of the attack is thus foiled (preventing the second stage of the attack from taking place as well).