People are downvoting this comment but I think it's a valuable assertion, and the core fact (JS engine developers use current/real-world empirics to make optimization decisions) is indisputably true: https://v8.dev/blog/sparkplug
If you'd simply omitted the bracketed clause, perhaps your comment might have been useful!
SSC wouldn't have a niche if they could get concepts across without a bunch of obscurantist bullshit.
People criticize SSC because they're like "uh leave it to the REAL experts", but A) it's just opinions and B) the 'real experts' are unreadable, so I'll continue to ignore them while occasionally checking out astralcodexten.