Your argument for selfish motivation does not hold water when you consider just how many decades came and went before an actual NBC was elected President, rather than one of the original citizens of this nation who were “grandfathered.”
You realize that the children of the Founders born before the Revolution weren't natural born either, don't you? The “soil” wasn't regarded as having possessed some magical property conveying eligibility to the Presidency before the Presidency ever existed.
The “soil” is the geographic territory of the nation, under the full jurisdiction of it. Mt. Vernon in Virginia was not on the “soil” of the United States in 1760. It was on English soil. That is because the geographic territory was under the jurisdiction of England.
That ceased upon the establishment of a new nation, the United States. At that point, Mt. Vernon became native “soil.”
That simply isn't true. I don't think you understood post 833.