The Insurrection Act of 1807 was "signed" into law a long time ago. Amendments to the act were "signed" into law a long time ago.
What Trump did, if he actually did it, was sign an executive order that invoked the Insurrection Act. The difference is not subtle.
Is it possible that he signed a Presidential Directive? Pres. Trump called them “National Security Presidential Memoranda”, and we may never know what it is?
https://www.loc.gov/rr/news/directives.html