Butter's fat plus the chocolate's hidden fat, over the flour. Under ~80% sets; over ~90% can't.
Rule of thumb from the post: butter is ~81% fat, a chocolate chip ~33% fat (cocoa butter). The verdict is about whether the fat can stay under what the flour can hold together while the starch sets — not about bake time. A rough guide, not a recipe guarantee — flours, chocolates, and ovens vary; provided as-is, bake at your own risk.