Signatures on important documents are often witnessed, and it's more about having some mark on the page that indicates 'yep I agree to this too' in case of disp

Signatures on important documents are often witnessed, and it's more about having some mark on the page that indicates 'yep I agree to this too' in case of dispute. You can pretty much write your name any way you like; as you say it would come down to an argument of you saying it wasn't you and a reasonable arbiter deciding how likely it is that the pages you're disputing have been added after the fact