The chapter structure comment is the most important thing they said and everyone skipped it
Buried in the editions explanation is the detail that Ultimate content unlocks as Jason and Lucia progress through chapters.
Chapters. Not missions, not acts, chapters. That is a structural word and Rockstar does not use structural words by accident. GTA V had a three act structure that nobody called chapters. RDR2 had six chapters and the whole pacing of that game came from them.
If this is chaptered like RDR2 then the story is going to be paced very differently from a GTA and I do not think people are ready for that.