This speaks to a general concern I have about this PEP. I like the syntax proposals overall, and I’m supportive of Python eventually adopting syntax like this for its typing system. But Python’s typing system is still evolving rapidly — I don’t feel like I have any ability to predict which new features might be proposed and/or adopted for Python 3.13. It’s currently pretty easy for us to add new features to the typing system, but adopting this PEP raises the possibility that a lot more typing features might require syntax changes in order to be well integrated into the existing typing system. We’ve already seen examples of this with PEP 696, where one of the questions asked has been “What would the proposed syntax look like if PEP 695 were adopted?”
I feel like I’d prefer to see Python’s typing system stabilise somewhat before we enshrine the current system (or something like it) in a series of syntax changes that will be very hard to reverse or change in the future.