What I've found with Wizz is they tend to kind of do whatever they want, sense be damned. I remember they dropped one of their routes for 2 months at some point, only for it to return (bit like Warsaw is this winter, except only Nov-Dec).
Cluj has varied from, if my memory serves correctly, which it probably doesn't, 2X weekly A320 to 3X weekly A21N, it's filled perfectly fine at all times. And honestly, there's nothing stopping them adding another weekly frequency at this point, or even dropping the route altogether on a whim, it is Wizz after all