Here is the actual rule. It is totally at the discretion of the umpire whether or not to call the runner forced off of the base out or safe. That is why that portion of the play is not reviewable.
i. The individual is touched by the ball (when not dead) securely held in the hand or glove of a fielder while the runner is not touching the base; Note 1: A ball stuck in a fielder’s glove remains alive. If the fielder tosses the ball/ glove combination to another fielder in time to complete a tag of a base or runner in advance of the base and the ball/glove combination is held securely, the runner or batter-runner is out. Note 2: If in the judgement of an umpire, a runner is pushed or forced off a base by a fielder, intentionally or unintentionally, at which the runner would otherwise have been called safe, the umpire has the authority and discretion under the circumstances to return the runner to the base they were forced off following the conclusion of the play. Exception—If a batter-runner safely touches first base and then overslides or overruns it, the player immediately may return to first base without liability of being tagged out, provided no attempt to run to second was made. Also, if any base comes loose from its fastening when any runner contacts it, such a runner cannot be tagged out because the base slides away (see 8-3-q).