Normally viewers won’t manually drag their browser windows to resize unless testing, but generally the theme will load as it should when it’s loaded in a browser window that already has it’s width established.
What happens with responsive themes is that they are coded with specific break points (the point of pixel width that things suddenly change to adapt). Each theme will have similar break points, but even 1px difference can make a difference. In your case, everything is set when it loads up, but depending on the break points, if you are simply dragging the browser window, you would just click refresh on the browser.
For this theme, when you view it in a desktop browser window, it’s in a normal layout. If you were to view it in a tablet, it will load to that specified break point that is most common for tablets. Same goes for loading it in a phone.
Hopefully that helped in understanding how media queries work? If you have a phone and a tablet, try your site out or the live DEMO for Seasonal and you will see what I mean.