Why automatically ascribe bad faith to people who study for coding interviews? They went to all that trouble to get better at something, so they're obviously diligent and seek self-improvement.
> Senior talent doesn't have the time or energy to push back on all of a systematically incompetent person's code until it's good.
That sounds like a problem with the company's timelines or priorities. If senior talent is so strapped for time that they can't insist on decent designs upfront, then they likely can't hire the right people either. Because even that takes time and energy. Mentoring juniors is part of the job for senior engineers.
It’s more than a full time job to push back on all of a bad hire’s output, and people are accountable for their own projects as well. Things inevitably get to “fuck it, good enough.”
First off, no, writing good code in an interview wins you additional points. Second, why do you think candidates can (or will) continue doing that on the job? New employees aren't allowed free rein to check in code from day 1 at most places - trust has to be earned. And I don't think any decent company allows check-ins without review.