Um. Taking time with smut isn't a rule. They clearly realised they loved each other since starting, and finally had a chance to confess about it abd they are busy people so they both took the chance to fuck. And yeah, according to the novel it is a lot abrupt and stuff. But works for me
I mean 23 chapters to develop this "thing" they have and then *BAM* full on sex scene? Bruh this left me bitter.