(The beginning after the end) Arthur and tess' relationship is kinda weird, Im not the only one who thinks that right?

I just finished the first two books of the beginning after the end and liked it well enough, but was kinda weirded out by where i thought the author was taking arthur and tess' relationship. In my head i was like no way, that would be weird and arthur says he sees her as a sister. Then i looked it up, and apparently shes his love interest and theres a whole confession and everything where he tells her they have to wait till she's older. I sighed very loud when i read that. Why does this genre of fiction (reincarnating into a younger body) have to be so damn weird about age stuff, the most egregious example being jobless reincarnater (where he's a legit pdf file and its so painfully disgusting) though tbate is nowhere near as bad as that, but why can't the authors be normal and not pretend its normal for grown ass men to be romantically or sexually attracted to literal children (regardless of how "mature" they are) it makes me question the authors' preferences. A good example for how regular people would behave is bog standard isekai, where the protagonist doesnt pursue a relationship with the 14 years old who has a crush on him (and he hasnt even known her since she was 5, what a great guy), sees his physical age groupe as nothing more than friends, and aknowledges that it would be weird to enter in a relationship in his current situation. the author also lets the teenagers act like teenagers and not just "very mature for their age". Don't know if this fits into progression fantasy, but couldnt find a better place to air it out