C.G.
I am a nurse midwife so deal with this a lot.
You don't mention when your ultrasound was. In the first trimester we don't change due dates unless there is >1 week difference. 2nd Trimester > 2 weeks, 3rd trimester >3. They are less accurate as the pregnancy goes on.
In reality, scans before 12 weeks are considered +/- 2 days, < 20 weeks +/- 5 days, and > 20 weeks +/- 10 days.
So it really depends on when this scan was done how accurate it would be.
You have the right to decline induction, your OB is someone you have hired to perform a service for you, they do not tell you what to do. But consider looking for a provider who will listen to your concerns and not ignore them.
Best of luck.