Will A Responsive Theme Not Have Dimensions Of Images Specified?

We've been messing around with the new Responsive Theme in version 4.1.4 and noticed that if we do the GTX now we get an “F” or “0” for the “Specify image dimensions” part. I am guessing but is this always going to be the case with a responsive theme? In order for it to be able to easily adjust I am guessing that it does not want to give an actual image dimension?

I used GTMetrix reports to show me the size the image was adjusted to in the desktop browser and changed my height and width on the Thumbnail settings to the adjusted size and that failing grade went away.