Touchdown Rule: a question

[THA]

I'm not an official, just a puzzled fan. Over the past few years I've noticed the expression "crossing the plane of the goal line" to indicate that moment at which a touchdown occurs. I've been following NCAA football since the 1950s and NFL since the 1960s, but unless I'm having a serious memory lapse I do not recall that expression being as prominent in earlier decades as recently.

I have the perhaps misguide impression that I missed the moment of a rule change. Is this correct? Did the expression "crossing the plane of the goal line" become more prominent because of some relatively recent change (in both the NFL and NCAA)?