The signing portion doesn’t have force of law; it can’t be cired in court.
It proves you wrong, and that is the point. You can't very well argue that a government excludes religion when the Top deity in the excluded religion just happens to be specifically referenced in the National Charter.
And by the way, what year is it? From what event are we measuring the years? What does Year Zero represent?
Too many people have learned a false history taught to them by people who didn't like the existing social structure and set out to deliberately change it, mostly with lies.
The reason we measure our years from Jesus is because of the importance to which he was regarded by the vast bulk of the society originating from Europe.
Christianity was as ubiquitous as Oxygen in those days, and it would have never been regarded as necessary to keep reminding everyone that the government was founded on and was expected to follow, Christian Principles. It would have been akin to constantly pointing out that the "Sky is Blue" and "Water is Wet."
In 1787, there were several states that still had official religions. This bit of fact is completely incompatible with the modern understanding of the relationship between church and state.