It could just be that they wanted to have the MC & main heroine next to each other, while the secondary male MC/heroine are off somewhere else. There could also be no reason as to why they're "paired" off.
For example, from three different events:
Spoiler:
These happen to be from before the series aired: Haruto/Shoko in front, L-elf/Saki in the back.
This happened not too long ago. There's most likely no significance in the characters places.