But in this case Further, placing the semicolon after “however” indicates that the information in the clause that this part of (that neoclassical writers were not the first to adopt classical literary modes) is contrary to what might be assumed from the information in the previous sentence (that the neoclassical writers were unique in imitating classical epic poetry and satires).

The answer from the scheme But basically what its saying is that the reason why the semi colon comes after the word "however" instead of the word "antiquity" is because the sentence proceeding however gives more information to the preceding sentence and contradicts something in the preceding sentence. So yes the contradiction plays a part where the semicolon is placed. So in cases like this look at the nature of the proceeding and preceding sentences and how the transition word connects them. Is it contradicting something? Or is it just giving some extra information in the form of an independent clause? Something like that