The Meteo France article I quoted is actually a bit misleading, it talks about a category 3 hurricane in a not really rigorous way «damages caused by this storm has been on par with the ones done by a category 3 hurricane» even tough you're right the sustained wind speed has been below the limit for a category 3. It's still strong enough to be classified as a category 1 (in england) or 2 in France.

The actual reason why it wasn't a proper hurricane was because this word is reserved for tropical cyclones. Neither the great storm or Ophelia are tropical.