There's no harm being cautious! The newly materialized form was Wang Baole's true essence body. He hadn't trusted Xie Haiyang completely. That had been why he had summoned a second avatar while keeping his true essence body safe in his storage bag.
He had his true form stowed away in his storage bag instead of having himself hidden far away. If his enemy had searched the area for him, he would discover his decoy first and not his true form, which had been hidden away safe and inside his storage bag.
It was akin to placing two spheres of light over one another. The first glowing sphere would hide the second sphere's existence. In fact, Wang Baole had gone to the lengths of injecting half of his essence into his decoy so that it would appear more realistic. Naturally, it was also considerably powerful.
Of course, the setup hadn't been entirely flawless. One would be able to sense that something was wrong upon closer scrutiny.