I picked up on that hypothesis immediately too, but via a different route.
If I'm correct...
What KATV, WIXT, and WJXT used is the "original" One & Only, based off of the 1978 iteration of the famous
image. I've seen a recording of WTOP using the cut in the WJXT open, there is a recording of a WIXT ID from '78 on YouTube with an identical logo/music to WTOP, and KATV's image song on the NMSA mentions how "we give it all we've got".
What WPLG and KSAT used is "Call it Home" jury-rigged to fit "The One & Only" slogan. The general melody to the news theme has the three-note signature, and the promo heard in image sample #1 for WPLG on the NMSA (and seen at the beginning of the reel) even includes the line "The one, the beat, where you can call it home..."
There is also this...
https://www.youtube.com/watch?v=id=xNKx9woVNjc;m=6;s=17