It is page builder functionality, and it is usual practice to set background image to cover container in order to have it covered all the time. If it isn’t set like that, image will resize on smaller screens, and because columns become taller, some portions of text (content) inside will be left without background. So, it is important to know that most of the time parts of the background won’t be visible. The actual visible portion will vary depending on screen orientation and width/height aspect ratio.
For instance, the common aspect ratio of portrait orientated tablets is 3:4 (iPad), and for desktop monitors it is 16:9 (full-HD resolution). In all instances the background is scaled to be as large as possible so that the container area is completely covered by the background image. In other words, some background clipping must occur, while the ‘content-safe’ area is the very center of each image – this area is always visible.
Keeping this safe area in mind, if you are using background as an important part of your visual message, make sure that its importnat part reside within that safe area so it won’t be clipped out.
All the Best!