Mr. James Madison, who had been a member of the Constitutional Convention and had participated in the drafting of the terms of eligibility for the President, was a member of the Committee of the House, together with Samuel Dexter of Massachusetts and Thomas A. Carnes of Georgia when the matter of the uniform naturalization act was considered in 1795. Here the false inference which such language might suggest with regard to the President was noted, and the Committee sponsored a new naturalization bill which deleted the term “natural-born” from the Act of 1795. (1 Stat 414) The same error was never repeated in any subsequent naturalization act.
I've read that entire piece (and I'd encourage any who doubt me to do the same) and nowhere in there does Mr. McElwee (who apparently wrote that article in 1967) provide a source for his claim of a "false inference" being found. That appears to be nothing more than McElwee's own individual conjecture as to why it was changed. He offers absolutely no evidence, no link to contemporaneous statements or Congressional records, to support that claim.
Looks to me like Mr. McElwee just didn't like George Romney, and wrote that article to argue against him being eligible.
If you believe me to be mischaracterizing this, please identify specifically the evidence that Madison believed there to be a "false inference". What contemporaneous document contains that proof? Again, here's the link for anyone who wants to check for themselves. The key language regarding the desire to correct a "false inference" is contained on p. 10.
http://natural-borncitizens.com/nbcfiles/nbc_McElwee.pdf