I don’t think the 1 second or less that it takes for the pitcher to deliver the ball to the plate would allow the center fielder much of a jump in to the shift.
I am an old school baseball fan but the game has evolved to identify unfair advantages to protect the game and the players: Balking, Taking out fielder at second base, Blocking home plate, Intentionally throwing at hitters, etc. The shift as it is currently allowed gives an unfair advantage to the defense.
Is shortstop a player or is it the #6 position on the field?
Is second base a player or is it #4 position?
When the shortstop fields a ball and throws out a player at first while playing in the #4 position, should it be scored 4-3 or 6-3? I think the numbers represent positions on the field and not the players. Obviously a player can leave his position to field a ball in another position but he must start from the general area of the position that he is playing.