Su Li spoke directly to Sun Yin, who did not hide anything from her.
Lin Yuan needed a family he could use as a tool. If he chose the Dragon Plum Family, he had to make this clear to them. He released such a message to intimidate both Su Li and the Dragon Plum Family.
Sun Yin was not worried about whether the Dragon Plum Family would spread this matter. Even if they did, it wouldn't matter. Sun Yin had already confirmed this with Lin Yuan.
If the news spread, it might not be a bad thing. Sky City's roots were far away in the North of the Lonely River, and those with ulterior motives would not be able to find any traces of Sky City through the Dragon Plum Family.
If this news spread, it would definitely attract powerful factions or experts who needed Grade 6 Creator resources.
Lin Yuan was willing to trade with such powerful experts and factions. This was because trading with these factions and experts would allow Lin Yuan to obtain great benefits.