Did the Iwo Jima bombing reveal the island's value?

Did sustained bombing tell the Japanese that Iwo Jima must be worth defending?

Pretty much; the intensity of the attack could itself underline the island's importance.

The extraordinary intensity of the bombardment would signal the island's importance. Defenders could infer that the attackers needed the target badly enough to sustain an unprecedented effort. That signal reinforced the practical reasons for improving underground positions and preparing a costly defence. An attacker can communicate a target's value even while attempting to weaken it.