I think I remember reading on a different site that the isekai thing was mentioned earlier in the novel version. Here it just kind of comes out of nowhere because apparently all the modern world was good for was preparing him for a math test. Which is actually pretty fair, too many isekai make it seem like it's easy to have the world at your finger tips because you used to browse Wikipedia before bed or some shit. Others straight up include access to the internet as part of the protagonists cheat skill, which is like the person/god responsible for the isekai in the first place saying "Please use Google-sensei to fuck my world up beyond all recognition."