I was worried about whether that whole number 1 thing would be hanging over their relationship so I'm glad to see it's likely resolved here. Obviously he has a complex a bit about this based on what he said about his sister, I suspect she's some genius that simply excelled without much effort in his eyes, so by recognising Shinomiya as someone like himself, someone who has worked hard to get where they are, it's essentially meant he doesn't need to resend her unjustly.
It's also interesting seeing the kind of family life he probably has. His parents seem to expect him to perform just as well as his sister and want him to follow the path they have decided. And living in his sister's shadow must not be easy if there is such a large difference in ability.