Do the Austro-Hungarian Erzherzog Karl ships count as second-class battleships?
Short answerPlausibly, but not as their primary role; the clearer model is a battleship able to combine battle-line and cruising duties.
NotesThe classification works as a plausible comparison rather than a firm primary label. HMS Renown explains the period category: a second-class battleship could perform battle-line duties while also taking on cruising work. That overlap makes such ships look like precursors to the later battlecruiser idea even though the contemporary designation remained battleship. Classification depends on intended duties and fleet context as well as armament and displacement.