Bill
I think this is not necessarily true (more polite than saying it is totally speculative) because had she passed any of these runners in said events they would undoubtedly have tried harder.
If you are winning an event you are going to win and all you need to do is not be passed, but if someone passes you then you suddenly are not winning and you undoubtedly try harder.
It is why world records and gold medals are won in races against competition.
Best wishes,
Graham