I don't think it is "reasonable" to assume that Congress simply had a flash of inspiration five years after the fact that "gee, I guess what we did five years ago was unconstitutional".
However, even if you do think that's a "reasonable" assumption, that doesn't prove it as a fact, and you can't build your "I am certain I am right" on a foundation that is based on nothing more than something being a "reasonable possibility". So, the elimination of the phrase "natural born citizen" in the Act of 1795 was nothing more than standard legislative housecleaning of eliminate redundant language in a statute.
You may not agree with that, but that's certainly as "reasonable" as assuming they all realized five years after the fact that they had acted unconstitutionally. In fact, if their motive was to correct an error, wouldn't it have been prudent of them to pass some clarifying measure to ensure that people born during 1790-1795 were not considered natural born citizens?
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.