I'd like to see that number quantified. Nonetheless, you'll see that I did not say "no HEDT user runs stock clocks" but rather, "almost no one..." I recognize that some HEDT users do not overclock.
You're free to do with your posessions as you choose. I choose a different path with my CPUs.
I've overclocked nearly every CPU I've owned since my first upgrade from a 486 to an AM586 way back in the mid-90's. Earlier this year I had a 7900x that I was planning to de-lid and see how far I could push it, but an opportunity to replace it with this (already de-lidded) 7960x came up so I took it. All-core turbo on this chip is only 3.6GHz, which is below my personal threshold for single-thread performance of at least 4GHz on modern chips. Ideally, closer to 5GHz but I'm not pushing this chip to 5GHz on ambient cooling. So I applied a moderate overclock to reach this desired level of performance and it is perfectly stable functioning in a system that is both a media server and video production workstation.
Multi-threaded performance of course matters (otherwise why buy HEDT?) but single-thread performance still matters also. For example, the decoder engine for VC1 is still single-threaded, so when someone queues up a VC1 video to play on my media server, I want to know the system can fill up the buffer fast enough to avoid stuttering/buffering. With base clock as low as 3GHz that's not a guarantee. Boost clock at 3.6 gets you closer, but I would rather have an over-engineered solution and not need the extra performance, than vice versa.