"In this case, Google is accused of relying on pieces of its code within websites that use its analytics and advertising services to scrape users’ supposedly private browsing history and send copies of it to Google’s servers. Google makes it seem like private browsing mode gives users more control of their data, Amanda Bonn, a lawyer representing users, told Koh. In reality, “Google is saying there’s basically very little you can do to prevent us from collecting your data, and that’s what you should assume we’re doing,” Bonn said."
It doesn't seem like the complaint is that Chrome collects data on you in "Incognito" mode, rather that websites (e.g. Google Analytics) still collect on you in "Incognito" mode.