Yes, the JIT (in fact, the whole “tier 2” IR (Internal Representation)) is new in 3.13, and so is the -X uops flag (and the corresponding PYTHON_UOPS=1 env var).
You are not expected to use the -X uops flag – it exists for the benefit of those core devs who are working on tier 2. I expect that eventually the JIT will be good enough to be always enabled, but not in 3.13.
I don’t think we’ll ever make the tier 2 interpreter the default, as according to our benchmarks it is not competitive with tier 1 – it’s the JIT (which uses the same IR but instead of another interpreter translates it to machine code) that is the long-term focus of our efforts.
I am right now assessing whether it makes sense to offer a build-time option to disable Tier 2 entirely – this could potentially make the tier 1 (traditional) interpreter slightly faster.