Job / Position description means something more... It means that your expected to do the task and perform well at it or you will be let go.

Generally you don't put those skills in a Junior PD, but you would expect a Junior to take on these tasks if they hope to progress. The Mid level PD would have it listed and as the junior shows they can meet each and every additional skill, the option of a promotion becomes available.

None of this seems hard for a junior dev tho... it just takes time, which I'm assuming the others workers don't really have with more pressing matters making this a great issue for juniors to grit their teeth on.

Note the words "on their own". They would be paired with a more experienced dev to collaborate with.

That seems self-selected and biased toward their own experiences.

When I was a junior I was allowed and given free reign to design the test system for the product and implement a design system for the frontend team.

Junior doesn't mean stupid, it just means less experience. How else do you expect people to gain experience if you don't give them basic independent projects?