This article doesn't do the best job explaining the broader picture - stability has been their number one priority up to this point.

- Most of the work has just been plumbing. Int/float unboxing, smarter register allocation, free-threaded safety land in 3.15+.

- Most JIT optimizations are currently off by default or only triggers after a few thousand hits, and skips any byte-codes that look risky (profiling hooks, rare ops, etc.).

I really recommend this talk with one of the Microsoft faster Cpython developers for more details, https://www.youtube.com/watch?v=abNY_RcO-BU