What did the Buddha mean when saying Anurādha "didn't actually find a realized one (tathāgate) in the present life"?

analogies are not perfect.

Don’t mix up nibbāna with remainder with nibbāna without reminder. The remainder is the body and mind freed from defilements.

Ideas are not craving. Anyway, the craving is cause of suffering, is the craving part, not the non existence part. It is due to craving that the non existence part is not possible, so it is an overreach. Eventually, we have to let go of the craving to get to nibbāna in order to get to nibbāna.

Idea wise I addressed it here: Nature of Parinibbāna - General Theravada topics - Classical Theravāda

Comparison of highest happiness wise, it makes no sense to downgrade parinibbāna with anything at all.