The [docs](https://developer.apple.com/library/safari/documentation/AppleApplications/Reference/SafariHTMLRef/Articles/Attributes.html) claim this:

> If the autocapitalize attribute is not present, the default value is sentences for <form> and none for <input> elements with type set to password as in <input type="password">. For all other form controls, the default value is inherited from the enclosing <form> element.

Nothing about autocorrect, fwiw