What makes you think they haven't benchmarked?
Here's one fun example from following development on Zulip: advapi.dll loads bcrypt.dll, which loads bcryptprimitives.dll. bcryptprimitives.dll runs an internal test suite every time it's loaded into any process. So if you can avoid loading advapi.dll, your process will start faster.
Are you talking about the cipher tests that are run when any cipher library is loaded?
There's a reason they do that and it's not for shits and giggles. You could find yourself with broken ciphers and not know it.
Skipping the cipher (or hash - not sure now) tests seem like a good way to get exploited.
Is there a source for this? My Google- and GitHub-fu turns up nothing.