A careful reading of official Major League Baseball Rule 6.08(b) suggests that in this situation, the batter would be considered "hit by pitch", and would be eligible to advance to first base.
The batter becomes a runner and is entitled to first base without liability to be put out (provided he advances to and touches first base) when --
(b) He is touched by a pitched ball which he is not attempting to hit unless (1) The ball is in the strike zone when it touches the batter, or (2) The batter makes no attempt to avoid being touched by the ball;
If the ball is in the strike zone when it touches the batter, it shall be called a strike, whether or not the batter tries to avoid the ball. If the ball is outside the strike zone when it touches the batter, it shall be called a ball if he makes no attempt to avoid being touched.
APPROVED RULING: When the batter is touched by a pitched ball which does not entitle him to first base, the ball is dead and no runner may advance.
In the description of the What-If, the ball does not actually strike the batter. Rather, some of the remains of the ball and the explosion strike the batter. Some remains also pass through the strike zone, some without. It is simultaneously a ball and a strike. Given the speed at which it's traveling, any
movement on the part of the batter, including respiration and heartbeat (or what little respiration and heartbeat can occur in that time) should be counted as an attempt to dodge the ball.
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