RTX 5080 rumoured performance

3DCenter forum did some manual frame counting using the digital foundry 5080 video and found that it is around 18% faster than the 4080 under the same rendering load.

Details here - https://www.forum-3dcenter.org/vbulletin/showthread.php?t=620427

What do we think about this - this seems underwhelming to me if true (huge if) , would also mean the 5080 is around 15% slower than the 4090.