Phillies games are never simulcast within the market. If the game is on NBC10, CSN will have other programming, but still feature Pre Game Live and Post Game Live.
Since the timing of the game can vary, the normal procedure is to have the next studio on standby. Normally, this is CSN (or TCN) waiting to go with Post Game Live. In this situation, it was likely easier for NBC10 to fill to the top of the hour with news rather than quickly add/delete commercial time to fit the slot. It's rare to have the game broadcast crew fill to the top or bottom of the hour for programming purposes.
Why? There are a few reasons. Suddenly putting together highlights to fill three minutes is not something they're going to want to do. If it's the last game in a series, and they are on a road trip, the goal is to close out the signal, pack the truck and get out of there. Also, if the game runs long and the satellite window is approaching its closing, they likely would not want to extend just to fill out NBC10's airtime. (This is unlikely, but possible.)