These articles never seem to include excerpts from said books. This is not sex-ed books they’re banning. There’s quite graphic depictions of acts of sex in these. I don’t think it’s unreasonable to not want literal children to read that kind of stuff.
Most Finns speak english pretty well, especially ones that are under 40 years old. However finding a job as someone not speaking Finnish can be a struggle. Fluent english skills alone aren’t something most companies would see as a big advantage as most people fresh out of school can pretty much do that as well. Finnish is a difficult language to learn but you don’t need to be perfect at it either. A foreigner willing to even try and learn the language is hugely appreciated. My russian neighbour knows like 30 words but that’s enough to get thru most conversations one needs to have with a neighbour.