I'm not trying to call out or belittle anyone but I always thought Athing MU was an 800/1500m runner. Even when she ran 49.57;and later spilt 48.3 on the relay, I was thinking no 1500m runner ever had her speed.
1.) FLASHBACK:. 2013-2017 Athing won 4 National titles in the 1500/mile ALL when she was 16 years old or younger
2.). Her 200m personal best Indoors is 24.11 (2019) and outdoors 23.62 (2018). A year or two before she dropped down to the 400 and set her personal best.
3.) Athing Mu started out as a more of a 800/1500m runner and did very well. She also posted a sub 18:30 country 5km performance a time most posters would consider VERY GOOD but Footlocker Championship material. Which demonstrates she still has amazing endurance off 800m training.
4.) Athing Mu is HIGHLY intelligent and she remembers her escapades at 1500m and wouldn't allow Kersee to move her to an event unless she was strongly convinced she could return to and be world class.
Athing ran those amazing 400m STRICTLY off endurance as she has never broken sub 23.5 for 200m. If a female can be world class at 800m and marathon, or pull of a 1500m/10000m double. Then surely a sub 50 400m runner Athing Mu can move BACK up to one of her previous events the 1500m.