I feel Sofia needs another arc focused on her for a "Sofia end" to feel justified. She unfortunately has to share her one and only arc with getting the series premise across to the readers. Meanwhile, Olivia seems to get more focus and screen time, as it seems she gets more "moments" sprinkled throughout the series, even outside of her arc. Sofia, on the other hand (at least to me), seems to flip flop between being 100% for a polycule, and being a little melancholic about not being the sole focus of Machino. Seriously, reread some of her conversations with Olivia and she ends up saying something along the lines of "Really! I love Machino too, isn't that great!"