None of what you're saying is wrong here, so I don't want to disagree.
But, I think this is just one perspective; i.e. moving to a cloud environment is one approach to providing a more circumscribed environment, but embracing endpoint sandboxing is another. For example, learning how to use Xcode is a fundamentally different (and easier!) sort of experience than learning the traditional UNIX development pipeline, due in large part to the fact that it provides a unified, discoverable interface. This is despite the fact that Xcode projects are actually substantially more complex than their UNIX-y equivalents, due to the high levels of coupling and complexity in the way that you have to interface with certain system services (signing with entitlements, bundle metadata, etc).
You still have to retrieve many resources from the cloud - simulators, documentation, SDKs - but the UI tells you that you need those things, and straightforwardly automates the process of getting them. Everything else that goes into a development project is not "environment setup", but a part of the Xcode project itself. Similarly, version control (a git repository) is nearly implicitly a part of the project. It's tricky to even create one without a VCS backing it any more.
Anyhow, Xcode is far from perfect - many of the places it touches the UNIX pipeline are extremely sharp edges you can easily impale yourself on (and don't get me started about codesigning) - but it nevertheless points at a different potential direction. For example; why expose the concept of a "virtual environment" directly at all? "New Project" could just create a requirements.txt and a setup.py for you, alongside a git repo and a virtualenv for that project. Or, the UI could be geared towards setting up a tox.ini rather than a virtualenv, and run everything through tox so it's in an isolated environment with defined requirements. This is a best practice anyway so why not make it easier to start early?
This might all be way too much work, but I think it's important to remember it's possible.
In the analogous Python tool, one could replace "per device" with "per project" - and perhaps have a "default project" so something useful could happen even before you've decided what you're doing...
... one could just put a little blinking red light on any jupyter windows whose kernels need to be restarted :) ...
I thought this thread was already interminable, I look forward to reading the never-ending rest of it now that you've raised the grim spectre of the PyPI user-ratings feature from the dead :).
I initially wanted to disagree when I read this, but I'm not actually sure what educational contexts you're talking about, and why "accountability" is important?
Oops. I meant to say "UI".
"beginner" is a direction, and not a fixed position; many people more "beginner" than the current audience could be well-served by a discoverable initial project-creation and REPL UI. While I don't doubt that some backend pieces might help (although I still don't see how the one being discussed would), I also think that it would be very hard to say that the back-end is a limiting factor in UX improvement for the Python onboarding process; the front end could move quite a bit up the value chain without touching any of the various backends it would need to interact with.
But of course, if I really wanted to make this point, I'd just write it; dstufft is certainly right that volunteer time is not fungible. If I'm lucky, I'll have the time to do that at some point, since my efforts to convince someone else that this is the high-value target have been failing for some years now ;).