https://www.chromium.org/Home/chromium-security/security-faq#TOC-What-are-the-security-and-privacy-guarantees-of-Incognito-mode-

"It is not possible for Chrome to offer the full Incognito guarantee for iOS. Some data is sometimes stored on non-volatile storage, and while Chrome for iOS makes a best-effort attempt to delete as much history as it can when in Incognito mode, the guarantee is not as strong as it is on other platforms. On Chrome for iOS, we therefore call it “Incognito*” mode."

We've removed the *, but I don't know the best way to rephrase this.
palmer@, you wanna take this one? :-D