Alright, I went digging. Google search turned up exactly two results for the phrase "combat as sport" before 2008 (incredibly useful to be able to request "before:2008"!) These are both academic works discussing literal blood sports, that is, gladiatorial combat as a sport. I don't think anyone here would recognize
that as being an example of "Combat as Sport" in the way intended for TTRPG analysis. Advancing in time, no reference occurs before 2011 that is not either the same academic sense, or one character biography. After 2011,
numerous new references pop up...and literally all of them are about 4e. (Notably, there is one false positive from 2007 in Polish. The
article is from 2007, but the
comment using the phrase is from 2011!)
Google Ngram provides essentially the same story. The terms
technically existed as early as the 1980s, from what I can tell, but only in academic media, with possible rare exceptions for describing a literary character who derives an athletic-like enjoyment from violent, no-holds-barred conflict: essentially, "war
enjoyed like a sport," rather than enforcing sport rules upon war.
So...no. The term does not "long, long" predate 4e, except in a completely different academic (or very rarely literary) sense. In the meaning of "violent combat
restricted by rules of fair play and sportsmanship," the term
specifically did come into existence in order to discuss 4e D&D, and in almost all cases, to do so pejoratively, usually in a vein similar to the "MMO on paper" or "button-mashing" canards. That is, by portraying 4e combat as
merely sport, it becomes less serious, less impactful, less intense, because who would ever claim that the Superb Owl is anything like the beaches if Normandy or the jungles of Vietnam? Who in their right mind could give equal weight to even a boxing match (where a hockey game is liable to break out!

) as they would to the Battle of Thermopylae or the Battle of Cannae?
I want to be clear, I understand that there are folks who, totally divorced from any and all edition warring stuff, find this legitimately interesting and potentially productive. I get that there are differences in tone and focus between Gygaxian murder-hole fantasy heistery and Heinsooic high-flying fantasy action, and that it can be worthwhile to explore how and why they differ and what can be learned from those differences.
I just think we should try to leave "Combat as War" and "Combat as Sport" behind when we do so. The well is poisoned. Let us brick it up and shift to the newer, deeper, cleaner wells that have been dug in the aftermath. This is, of course, my personal stance. The only person "required" to heed it is
me, and between you and me, I'm not real confident in his consistency. But it genuinely seems to me that we have legitimately
stronger alternatives that lack the baggage.