This "Report". "Leak" or "Rumour" is complete and utter garbage.
Here is the best estimate for the 12900K performance in CineBench R20:
1) Single Core 745
2) Multi-Core 8,620.
If the 12900K uses exclusively DDR5 memory, then the gaming performance will be below that of the 11900K
Without overclocking and staying completely within specs, my 5950X gets a CineBench R20 score of around 12,100 whereby my ambient temp in the room is 30 degrees Celsius (87 Fahrenheit) and I am using non exotic cooling (360 Rad AlphaCool Eisbaer).
There again, as opposed to the Tech Media or Tech YouTubers, I put in the months of work to actually learn how to configure 3rd/4th Gen Ryzen CPU where they - even two years after launch - are still oblivious.
I documented how to configure 3rd/4th Gen Ryzen in an article I posted on the AMD Red Team forum almost a year and a half ago in March of 2020.