I had the same issue, and found no info regarding how to solve it for iOS devices (any browser).
So I've inserted a jquery to scroll down when the url parameters have the string submissionGuid - parameter present in all hubspot form submissions.
Add an ID or Class to the section where you display your inline message. i.e. id="AREA_INLINE_MSG"
 
Insert the following code when the page is ready:
 
if (window.location.toString().indexOf("submissionGuid") != -1) {
    $("html, body").animate({
        scrollTop: $("#AREA_INLINE_MSG").offset().top + 3000
    }, 1000);
}
Note: I've added 3000 pixels to the window position to scroll down a little bit more.