For those holding out hope that the crown jewel isn't Shakky, I'd advice to curb those expectations

coz for 1 the phrasing "treasure/crown jewel of hachinosu" comes off across as something that everyone was aware about an ornament/a source of pride. It doesn't really make sense to describe a DF or even an ancient weapon in this manner. Hell you'd think that only a select few Rocks Pirates would even know about such a ting. So the most logical fit for this imo is Shakky, the idol loved by everyone who came to settle and setup a bar on Hachinosu.
Then there's Garp's dialogue with Sengoku about the Rocks Pirates reaction being predictable given their crown jewel was stolen from them as though he's saying that it was public knowledge. That in addition to Whitebeard's comment about Rocks when he said that "He knows Rocks is going to lose focus on their objective".
That very much sounds to me like the main objective for the raid on God Valley was to resuce Shakky who was stolen. However we know that the WG also had a shit ton of rare devil fruits up for grabs and we also know that Rocks was searching for one other Devil Fruit aside from the one on Elbaf so Newgate's comments might have been referring to Rocks losing sight of "Shakky" for "the rare devil fruits" on god valley.