The first thing that hit me here was that the PU did the right thing in getting out to cover the play. Being human we umps do make mistakes (GASP!) from time to time and when your partner at the plate is doing his job and getting out to make the call it makes you both look better, much better!
Never assume you partner, BU or PU, will always be in position to make the call. Things happen. A partner can always fall down, get blocked by players, make a mistake and go the wrong way, what have you. It's a pleasure working with a partner that works with you as a team!