Wait, did you compare the top of the line 16-core i9 against the 6-core midrange Ryzen 5? It may be the number we have, it may be someone else's comparison, but you did write both numbers saying it's a 30% difference even though they are completely different.12900k 8core=1511:8cores=188=6% less performance than single thread.
(which can be compensated for with a bit more power which we can see form the O/C numbers)
New zen 4 (might not be accurate) 1329:8=166=30% less performance.
(And that's just 8 cores, not the full 16 cores difference)
Here's the fair comparison: the supposed Ryzen 7600X versus the i5-12600 (non-K, with 6 p-cores and no e-cores). This puts 6 cores against 6 cores. The Ryzen gets 1329 points, the i5 gets 1063 points.
Or take the top i5 versus the Ryzen: 1244 points against 1329, now using two e-cores to help.
Always use apples-to-apples when possible, and in this case, it is possible.