From the replay of Boss we saw...

Rather than he reverted back to a child, it's more like... He turned into someone completely different.

It's possible that Boss was possessed by someone with the ability to control someone else's body or Stand.

The Stand that I thought wasn't Boss's was actually Boss's Stand...

And the one that I thought to be Boss was actually not Boss...?

I... found it...!

It's... here...!! Finally...! I... found it!

I found....

...iiiiiiitttttt.

Squalo was curious about what Narancia has found, but he now refrains from making unnecessary action because he was scolded from making a ruckus earlier.