My phone (LG G2) has a viewport size of 360px 598px. Col-xs aims devices smaller than 768px, so that means that wether the user is in portrait or landscape mode, he will have the same result, even though in landscape mode i could display more elements due to its larger width. That's why i wonder why the smallest media query is 768px in bootstrap, which doesn't take into account phone's portrait/landscape view.
Thank you for any clarification.