Never seen this before

[alex7]

From OBR:
Rule 9.02(c) Comment: The manager or the catcher may request the plate umpire to ask his partner for help on a half swing when the plate umpire calls the pitch a ball, but not when the pitch is called a strike.

The manager may not complain that the umpire made an improper call, but only that he did not ask his partner for help. Field umpires must be alerted to the request from the plate umpire and quickly respond. Managers may not protest the call of a ball or strike on the pretense they are asking for information about a half swing.

Appeals on a half swing may be made only on the call of ball and when asked to appeal, the home plate umpire must refer to a base umpire for his judgment on the half swing. Should the base umpire call the pitch a strike, the strike call shall prevail.