The story behind this lesson
This lesson was not mine. It was taught to me by a student with exams and no time, who tested the proposal tool and refused, politely but firmly, to let it speak for her. She flagged every place the draft promised something the facts did not support. Her complaints were worth more than any feature I would have added alone, because they were evidence someone cared enough to read closely.
So I changed the rule the tool follows: it writes from the details you provide and invents nothing. The guarantee section is now optional and clearly marked editable — delete it if you do not offer one. A proposal you can stand behind beats a impressive one you cannot.