There seems to be a lot of Elementor bashing going around lately, especially from people who use other builders. When they had the bugs in v3.0 it was justified (they owned up to it though). But this statement is simply incorrect, see the same blog you referenced to from almost a year ago: https://elementor.com/blog/introducing-full-site-editing/

“full site editing” is something you do. Trademarking it would be like trademarking “web design”. Come to think of it.. 😀