I disagree, it IS hard to believe a super talented and well conditioned 21 yr old could do that in such a short space of time.
Comparing Warholm, who ran 2 races, to her 3, when he is at his absolute physical peak and she isn't, is just not the same at all. I have seen many times an athlete run a 400m and 200m within a fairly short time period (and yes, Femke Bol has done this with some success) but I do not know of any 400m/400mhurdler who has run 3 x 400m distances in those quality times in that short space at all, ever, not on the professional circuit.
Anyone that saw Perec, probably one of the, if not the, greatest 400m runners of all time, win her 96 Olympic title in 48.2 could see she couldn't even get up off the floor for an age. She wasn't running that after a 50.0 and a 53. as well.
All these crazy trebles that NCAA athletes do are never reproduced when they get to the professional circuit or at a Championships outside the NCAA. Have they destroyed their careers by over doing it at the NCAA; did they peak too young, or is it something else?
For me, it's a combination of all 3, and I don't like it.