Is there a single, more generic term that can be used to describe both a row and a column? In English, we can refer to a line as being horizontal or vertical, but unless we say ‘a line of something’,
To speak of a vertical row would seem somehow perverse. It would seem far more meaningful to speak of arranging things in a vertical line—to distinguish this line from some other possible line in a different orientation. (It might seem even more normal to speak of columns, but that is outside the scope of this Question.)
And indeed, there are scripts with vertical line direction that differ in the "direction of line progression". For example, most asian script progresses right-to-left, while mongolian script progresses left-to-right. It's this "direction of line progression" that's usually conflated with "directionality" and which I try to untangle.