The packaging metadata Requires-Python assumes PEP 440 version numbers, ordered in the “natural” way defined in that PEP (alphas before betas). In practice, I doubt having a “mixed” alpha and beta ordering will actually affect anyone in that context, but it is technically a violation of that spec. I could imagine, if the rolling release PEP gets accepted and projects supporting the beta releases becomes common, Requires-Python: >=3.10.0b2 could be a spec we’d see in the wild. And if 3.10.0a3 doesn’t conform to that spec, even though it technically should, someone may potentially have a problem. (Yes, I know, “you’re using an alpha, so expect breakage”…)
Overall, mixing alphas and betas like this seems like a fairly gratuitous violation of an extremely common convention, and while we can argue all we like that it won’t affect anyone in practice, it’s still going to break a lot of assumptions.