Apple chips don't have AVX-512.
They do have media engines (that don't support AV1 encode), so if you switch to H.265, it will pull way ahead.
Zen 4 isn't 512 bits wide though, it's a split cycle 256 bit wide SIMD engine otherwise very similar (except in register size) to M6's.
The answer is more that Geekbench is at this point[1] heavily tuned to exactly the code Apple silicon does well: implicitly parallel wide-issue scalar code that you typically get out of modern compilers and JIT engines when throwing mostly-unoptimized "regular source code" at them. Apple has an enormous amount of instruction issue parallelism compared with x86.
The grandparent is looking at transcoding tasks where the limit isn't instruction issue but actual compute hardware on the core. And Apple doesn't actually win by much there.
It's just hard to know what to measure. Geekbench tends to be a metric for "feels fast doing boring interactive user stuff", which probably matches Apple's marketing imperatives well.
[1] Really they keep moving harder in that direction with every release. The "cooling pauses" in v6 likewise seemed very much like an attempt to boost the score on fanless Apple devices. If one were the type to allege a dark conspiracy, this is a tempting spot.
MacBook Air/neo are the only ones without fans. Even the Studio Display has a fan
Now... you can make a reasonable case that this matches real world interactive load better. But it also happens to have the practical effect of making Apple's numbers better, and no one else's. The new benchmarks are measuring subtly different things, and the new thing they measure happens to be what Apple wants to sell. At best, that's backwards.
GB's author, John Poole, has stated the intent of Geekbench CPU is to measure the CPU and CPU alone, as in he doesn't want to measure limits caused by the form factor of the device the CPU under test is embedded in. Since GB runs on phones, that means he had to implement the cooldown pauses.
Intel's turbo boost means this GB feature almost certainly inflates lots of x86 scores too, even with fans involved. Not sure why you're being so conspiratorial about it.