On Chrome for iOS, due to platform limitation regular and incognito* tabs share HTML5 local storage, which is typically used by sites to store files on your device (client-side caching) or to provide offline functionality. This means the same sites can always access their data in this storage in both regular and incognito* tabs. Incognito* tabs will still keep browsing history and cookies separate from regular tabs, which are cleared once those tabs are closed.
Google did push an update to the app on Wednesday for “stability and security” issues, but it doesn’t seem to have addressed this bug.