Nah bro, I thought that at first too but the bottom literally say it here
https://www.mangago.me/read-manga/pond_with_flowers/uu/br_chapter-304206/pg-26/
I think its the bottoms parents that are betas which is why its really weird for him to be an omega. Either that or the author made a mistake and the dads trait is up in the air.
Exactly, if a child noticed theres no way an adult wouldnt be able to. And we know via the friend that it was intense and constant. He easily noticed after only a couple minutes of talking. So either these kids were left alone so often that the dad didnt notice. Or the dad noticed and just didn't care. Either way sketch as hell.

Ok so I just read the whole thing through, and quick question. The dad's an alpha right? So why the hell did he not notice his son smothering his step son in his pheromones? Like a child knew that it was extreme but the father didnt? Sketch as hell if you ask me