Sometimes the translations aren’t very elegant since we prefer that they correspond to the Swedish sentence than be 100% elegant. If you change too much of the sentence, then it’s not possible to translate anymore without knowing why those changes are made. And the course is directed towards beginners of Swedish. It’s always a balance, but I prefer the literal translation here, otherwise it would have said something else in the Swedish sentence.
I wasn’t involved in translating, but we trying making the English translations as good as possible, but you still want to keep the 1:1 translation from Swedish as much as possible, which means it’s not always 100% perfect since you want to get the Swedish structure across as well. Try sticking to what it actually says in the Swedish sentence as long as it’s acceptable English.
på konferens is a very general statement, meaning you're not referring to a specific conference in the sentence. If we were thinking of a specific conference, we'd say på konferensen.
There are some cases when article use differs between Swedish and English in this way. For instance we often say har bil to say that someone 'has a car' in a more general sense, which almost gets close to 'is a car-owner' in meaning (although of course that in turn has a closer back translation into Swedish, too). We can also say har en bil, that just puts a little more focus on it being one specific car.
It's also possible to say in Swedish that professorn är på en konferens but it's just more idiomatic for most situations to say på konferens if you mean he's at 'a conference'.
Thanks for the clarification. To an English speaker, unless the article 'a' is specified, indicating a generic conference, it implies that the listener knows which conference the professor is actually attending. I saw that it wasnt en konferens, so took it to mean konferensen..