Well the first 4-minute mile was achieved in a similar manner and for some reason it is well known in the popular imagination. To be honest I think these arbitrary marks of achievement are all very artificial and more about good PR more than anything else. Personally I think the 2 hour marathon is slightly less arbitrary than the 4-minute mile but breaking it was only a matter of time.

No, it was a genuine race (the 'pacemakers' were also competing, were not lapped, and had to finish the race).

They completed the race (not hard to do when it is only a mile) but please do not try to suggest that Chataway or Brasher were in that race as anything other than designated pacesetters and windbreaks for Bannister.

Sure. But to pace Bannister on e.g. lap 3, his pacemaker had to run those 3 laps at wr pace. And Bannister had to run the final lap alone.

they did not have an suv to draft behind, and the pacers had to keep up from the start

This doesn't make it any less artificial or arbitrary. The marathon is a different beast from the mile and it doesn't make much sense to compare two different eras.

of course it is somewhat staged for optimal conditions, but still an amazing achievement. It's not an official world record and everybody is aware of that.

Would a treadmill be safe at that pace? 13mph is extremely fast especially over a sustained period of time.

Here is Haile Gebreselassie demoing a 4 minutes per mile pace on a treadmill: https://www.youtube.com/watch?v=YSp1r1QhUSY

I don't know how safe it is, but people have done times in that general speed range, e.g. Eric Blake's 2:21:40: https://www.recordholders.org/en/list/treadmill.html

2:21 is not even in the same ballpark as <2:00. 2:21 is a very respectable time, but not even international/national standard. It's a chasm.

When you're talking about treadmill speed and the mechanics of that (which we are), it's definitely in the same ballpark. In terms of running, no.