I think the last couple decades of software suggest that all these indicators, if adopted by companies that significant numbers of people wanted to work for, would quickly become checklists of things to do/fake.
See also: college admissions. (No, that kid probably didn't do that volunteering activity because they wanted to help people, but because they were told it was a checklist item, as they were coached through college admissions. And they probably didn't learn anything, and they were coached on what to say about that in the essay. And, normally, actually productive volunteering probably wouldn't have looked like each one of those kids starting their own duplicate initiative so each could spin it as demonstrating leadership. And it's more an option for kids from families well-off enough that the kids didn't have to work jobs that would contribute better to their household income or college expenses. And don't get me started on how the well-to-do decided that "travel" would be a plus on applications.)
Next level: You take interview vacations, where you work 3 days for every final company in your interview round. It’s an exchange: You check the cushions on the sofas of the HR ad, they check that you can actually take a bugfix to production.
Even so, it's probably not going to be super-effective, unless each workplace is willing to have enough useful small things that do not require knowing substantial chunks of the existing code base.
It is probably realistic to expect someone to write something useful (although possibly small) in three days. It is less realistic to expect someone to write a useful component integrated in a large system that they have to learn, in three days.
They need to be contrived bugs. Unpaid work is illegal in the US, and most other 'civilized' counries. Plus you don't want your competitors to send someone to interview just to look at your code.
Is that actually true? It's probably uncommon in tech but I understand it's fairly common in creative fields and--while it was a long time ago--I worked a couple unpaid internships when I was in high school in chemistry labs.
The trick is it can't be work, only work like things of no value. You can have unpaid internships so long as you are getting training and not doing valuable work.
A railroad engineer intern can move cars around the yard all day, assembly trains, and other such things. However if they move the car to a loading dock where it is loaded/unloaded that is valuable work and must be paid. If the train they assembly leaves the yard for the next that is valuable work (unless they all make it back to this yard unused).
Most companies choose to pay interns rather than figure out how to not break the rules. A few have a separate intern program where they carefully figure out tasks to assign interns for training. If your intern program did valuable work you should talk to a lawyer.
Surely there is some economy of scale here, where a standardized first round interview'taking a bug fix to production' fits multiple companies. Noone should have to do more than one technical interview
Why not skill at writing 8-legged essays[0] instead? Either way, you're so far away from anything that maps directly on to "is this person likely to succeed as an X level software engineer at Y company" that it's all pretty arbitrary.
Not to mention, you'd have to have a precise and well defined notion of what "analytical hobbies" are. Preferably one that doesn't carry an inherent classist[1] (and maybe even racist or sexist) bias. That part alone seems pretty tough, forget the actual definition part.
