Giants - Redskins

[Zeke5]

I didn't see the game but I'm assuming that this happened
within 2 minutes of the half (It's not too common for a QB
to spike the ball to conserve time outside of 2 min)

Within 2 minutes to the half the replay official, not the
coaches, has control of signaling to the referee that he
must review the play. Since it sounds as if Washington was
trying to hurry up and conserve time, the replay booth
had an abreviated review and signaled to the referee. The
referee probably determined that the signal came just
before the snap and proceded with the review of the
previous play because he did not have enough time to
react and kill the play.

Just guessing ...