To your edit, you are still making an assumption of pettiness on the part of God. These "swear" words are nothing but wind. They have no impact on the world.

To your edit, you are still making an assumption of pettiness on the part of God. These "swear" words are nothing but wind. They have no impact on the world. If God is invested in the world, then is probable that only those words, idle or not, that made a positive or negative impact on the world would be worthwhile to judge with any weight. So-called "idle" words may have been mentioned simply to cast an umbrella over all speech, due to an incomplete recollection of what the Christ figure had once said about speech. Like most attributions in the new testament, it is a second hand account of what had been said a decent while before.