Most likely it's differences in setup of their HD radio exciter, although it could be differences in the encoding schemes they use to get the signal from the studio to the transmitter. There's typically a LOT of delay (like 8 to 10 seconds) between real-time and what's broadcast using today's various digital schemes. It's not surprising that two paths from the same source are not the same.
95.7 shuts off their HD during home games for this very reason. Back when the A's were on Free FM the delay was really bad - about 15 or 20 seconds. It was really strange to be in the concession area (where they're playing the radio) and hear the crowd go wild above, then maybe 15 seconds later you'd get to hear what happened.
Dave B.