This style is very useful to add to sites for use on calendar and news archive pages, as well as have available anywhere else on the site where you would want the stacking order of a row reversed on mobile. This row style can be applied only where needed. This can also be applied on the master layout for sites that have a left nav and a page content area under the left nav that should show below the main page content area.
The CSS in the first option reverses the order of all columns, so naturally if you had 4 or more columns they would all be stacked in the reverse order, which may not be desired, but this row style can be applied on a row by row basis. If you only want the last column affected, use the 2nd method.