Honestly going to lose my mind with how people don't understand basic physiology behind track events.
Short summary: holding up an 8:33 woman like Welteji and extrapolating 1500 times for a 400/800 runner is totally useless. Would be comparable to predicting Welteji running a 50.0.
Long summary:
The sprints overwhelmingly use anaerobic alactic (pure sprint power which lasts less than 15s) and anaerobic systems (going pure anaerobic last max 2min).
Events 1500 and over use a large majority aerobic energy.
The 800 is the cross over between these systems meaning you can approach at like a distance runner (eg Faith Kipyegon/Sifan Hassan who are 1:57 or better but also 14:30 or better 5k women), as 400-800 runners (eg Mu, Rogers), or as hybrids - low mileage but not sprint focused like Brazier, Giles, Wilson, or Bishop.
The further away you move from the energy system that underpins your success the worse you do. That's why despite Welteji, Muir, Hassan all being barely 1s off Mu's 800 PB, none of them have for a second considered doing the 400! That's because they approach it with training that is aerobically focused (they're all 8:33 or better in the 1500). I'd be surprised if any of them could break 54 from blocks.
Same idea, Rogers can do a 52.04, but hasn't broken 4:10. Mu 49s 400 but 4:16 1500m.
Hybrid athletes peak in the 800 but can run average to good in the 400/1500 but not world standard in either - eg Brazier (47/1:42/3:35), Arop (46/1:43/3:38), Wilson (53.6/1:55/4:05), Bishop (54/1:56/4:04).
It is staggering how many people in this conversation don't get that.