There is virtually no space at all between the cabins in the load and unload area -- certainly not enough space to insert another cabin. The cabins speed up slightly as they leave the unload area to open up some space between them thru the turnaround, and decelerate to close up that space as they enter the load area.
The way the 2nd loop works is that there are 3 positions. There are 2 cabins in the loop, at position A (presumably unload) and at position B (load). When loading is complete, those 2 cabins simultaneously move forward to positions B & C. A few seconds later, the next cabin enters the loop from the main unload and stops at position A, creating a gap on the mainline. When the gap reaches the exit from the 2nd loop, the newly loaded cabin leaves position C, filling the gap, and the loop is back to 2 cabins where we started.
View attachment 411529
BTW, there is no pushing of cabins in regular operations. All cabins in the station are driven by tires above the track which I assume are controlled by the computer.