I HATE the WA rules book so these are from the USATF book. The rules are the same just worded differently. RULE 163.5 Each competitor must keep in the lanes outside the line or curb marking the inside of the track, including the curved part of the diversion from the track for the steeplechase water jump. In races run entirely in lanes, each competitor must keep in the allotted lane from start to finish. In races run partially in lanes, each competitor must keep in the allotted lane from the start to the marked cut-in points. Unless a material advantage has been gained or the athlete is in violation of Rule 163.4, a competitor shall not be disqualified if he or she: (a) Is pushed or forced by another competitor to step out of the lane, or (b) Steps out of the lane on the straightaway, or (c) Steps or runs outside of the outer lane line on the curve, or on any straight part of the diversion from the track for the steeplechase water jump.
79:25 of feed, 8:18 of race
https://stream.nbcolympics.com/track-and-field-session-6-integrated-feedBased on the wording of the rules, I can only assume either (1) the umpire did not see the infraction and did not write up an official report to give to the referee or (2) the referee decided that there was some sort of contact that caused her to step inside the rail. Watching the the video, I do not see any contact; it looks like she just stumbled as she came off the barrier. It looks like a clear DQ to me. Sometimes things just get missed in a track meet just as penalties are sometimes missed in a football game. And just like football, they cannot go to the video to determine if an infraction occurred; it must be reported by the umpire first. If a football official misses an interference call, they cannot check the replay video, see the penalty, and enforce it. If the flag was not thrown, it never happened (even if it did).
Elle Purrier in 1500 final at Trials
https://www.youtube.com/watch?v=SZETvwdhofs&t=85s(1) Purrier did not step inside the rail; she was pushed inside the rail. See rule 163.5a above. (2) She stepped out on a straighway. See rule 163.5b above. No DQ for her.
I have not seen the video of Niyonsaba. I watched the replay but did not see her step inside. Does anyone have a video link that shows the infraction?