For those curious, the fine print...
DQ seems to hinge on whether advantage is gained. The athlete is also required to expediently return to the track.
IAAF COMPETITION RULES 2018-2019
(a) In all races run in lanes, each athlete shall keep within his allocated lane from start to finish. This shall also apply to any portion of a race run in lanes.
(b) In all races (or any part of races) not run in lanes, an athlete running on a bend, on the outer half of the track as per Rule 163.5(b), or on any curved part of the diversion from the track for the steeplechase water jump, shall not step or run on or inside the kerb or line marking the applicable border (the inside of the track, the outer half of the track, or any curved part of the diversion from the track for the steeplechase water jump).
Except as stated in Rule 163.4, if the Referee is satisfied, on the report of a Judge or Umpire or otherwise, that an athlete has infringed this Rule, he shall be disqualified.
An athlete shall not be disqualified if he
(a) is pushed or forced by another person to step or run outside his lane or on or inside the kerb or line marking the applicable border, or
(b) steps or runs outside his lane in the straight, any straight part of the diversion from the track for the steeplechase water jump or outside the outer line of his lane on the bend, with no material advantage thereby being gained and no other athlete being jostled or obstructed so as to impede his progress. If material advantage is gained, the athlete shall be disqualified.
Note: Material advantage includes improving his position by any means, including removing himself from a “boxed” position in the race by having stepped or run inside the inside edge of the track.
This Note specifically outlaws the practice of an athlete seeking to improve his position in races by moving onto the inside of the track (whether intentionally or after being pushed or jostled there by another athlete to get out of a boxed position by running on the inside until clear.
Whilst normally running on the inside of lane 1 in the straight (as distinct from doing so on the bend) would not lead to mandatory disqualification, the Referee now has the power to disqualify in his discretion if this occurs and the athlete is advantaged even if the initial reason for being there was the result of being pushed or jostled.
...the athlete should take immediate steps to return to the track without seeking or gaining any advantage.