I don't see how Jim Ryun could be credited with 1:44.3 when he was never recorded as running 1:44.3.
No one put a stopwatch on it.
When Jesse Owens broke the world record for 200m during a 220y race his time for 220y was his official 200m record. They didn't knock a tenth of a second off of his time because it was presumed that's where he passed 200m.
Further, Ryun's time would have equaled the world record but he was never credited with the world record.
And even further, Ralph Doubell did run 1:44.3 for 800m two years after Ryuns 1:44.9 880 and Doubell was credited with the world record.
And even further still, Dave Wottle ran 1:44.3 fours years after that and was credited with the world record.
If Ryun had a verified 1:44.3 he also would have been credited with the world record.
The world record they were tying?
Peter Snell's 1:44.3 recorded en route to an 880. (1:45.1)
Yes, Ryun's 800m time was surely passed in 1:44.3 or better.
But if it is not recorded it is not a record. You can use extrapolations.
For personal bests, the IAAF doesn't dig deep looking for verification of everyone's PR's from 50 years ago.
Thankfully Brazier has cleared this all up.
Oh and I got to see Achon's 1:44.55 in person. Huge kick coming from behind and then running away.
Not superior to Ryun but it was clocked.