Very thorough evaluation and you are probably right, but I've seen so many inaccuracies and contradictory splits for races during this era, and without complete video evidence, I think a lot of the splits are suspect.
Ryun's 3:51.1 Mile supposedly had a 52.5 last quarter. Well that's what has been quoted in various books over the years. Then there appeared a Youtube video of the race showing it was more like 53.8.
The Miler's book I mentioned is a T&FN publication and Nelson is co-editor, so the 2:48.7 comes from him and the pages of T&FN.
It has his last 880 as 1:51.3, 440 as 53.9, last 100m in 13.5.
That's what, 1:50.7 for 800m and 53.6 for 400m? It also gives his last 300m as 39.3
In The IAAF World Record book, which still has Ryun's wrong split of 52.5 for the mile, it gives 100m splits! How many timekeepers did they have? If it was a 440yd track with 220 marks, how can they give such accurate 100m splits? You rarely get such splits even for 21st century world records.
The IAAF book gives his last 800m as 1:50.5, last 400m as 53.3, last 300m as 39.6. Everyone 0.2 or more different from the T&FN account.
I've also never seen the leader's 300m time given as 45.5. Why would they take such a time. Surely they would either have a mark at 330 yds after the start or else theyd have taken the split at the finish line, which would have been 320yds into the race, wouldn't it?
And if Ryun's 440 split was 60.9, which gives 60.5 for 400m, then doesn't a previous 100m of 15.0 seem more likely than 14.0, which requires a very fast increase in pace from so far out?
It's a shame there is no video evidence showing the runners go through the finish line on the first lap. I think the fact it was a 440 yd track rather than a 400m track might have thrown up some somewhat ambiguous split times.
Certainly there is a lot of confusion and disagreement on this race from sources I've seen.