I guarantee this is the case. If their desktop effort at a "new browser" is a chrome extension, no way is the IOS version anything more than a wrapper around UIWebView.
It's going to perform terribly compared to Safari. As far as I know, Nitro is turned off for UIWebViews, which means JavaScript performance will be at 2006 levels. UIWebViews are for showing simple HTML content and maybe running some simple JS code, not for actual browsing.
Additionally, Yahoo! has never called it Chrome killer.