I like it! We may quibble over what the time limit should be, but I think that doing coding challenges this way is the most inclusive and fair way to do a coding interview. All candidates do the work in their own environment, so one doesn't have to make an exception for, as one example, a blind person who can't write on a whiteboard. It's also more inclusive for potential interviewers; consider the challenges involved in a blind or visually impaired interviewer watching a candidate code in real-time. This way, the interviewer doesn't have to watch in real time, just as coworkers usually don't watch each other in real time on the job. Unless the team does pair programming, of course.
To take it all the way, I think the follow-up discussion should be done strictly in text, using some combination of IM and a web-based code review tool. So the interviewer would call out parts of the PR and comment on them through the code review tool, and the two could have more free-flowing discussion over IM. Again, this would be just like the way it's actually done on the job, at least in my dream all-remote environment.
To take it all the way, I think the follow-up discussion should be done strictly in text, using some combination of IM and a web-based code review tool. So the interviewer would call out parts of the PR and comment on them through the code review tool, and the two could have more free-flowing discussion over IM. Again, this would be just like the way it's actually done on the job, at least in my dream all-remote environment.