The Deferred Prosecution (DP) typically only requires a IID for 1 year, that is and has always been the case. Courts can order it longer if they want on a DP. However, the Court is not the only one who can affect your license with their order, DoL has their hand in it also. You likely did a DP because you previously were convicted of a DUI,or were convicted of a lesser crime after being originally charged with a DUI. The fact that DoL says 5 years for the IID also tells me that the prior DUI was a conviction for DUI and not reduced because the statue on DUI convictions states that the first time a IID is "ordered," (typically for a first offense DUI conviction) DoL shall require and IID for 1 year, and upon the second time a IID is ordered DoL shall require it for 5 years, and for the third time it is ordered it shall be for 10 years. So in your case, you were previously ordered to have an IID for 1 year due to a DUI conviction, making this DP a second time you were ordered (as a basis for the DP). So even though the court only requires it for 1 year, it is an order of the court nonetheless, and therefore DoL treats it as a second IID order and that takes you to 5 years.
Good for you for complying with the IID requirements and having no positives, I hope your program/treatment is going well. I always tell my clients, it doesn't hurt to ask DOL and the court, all they can say is no, but in this instance I agree fully with the previous couple of answers. The DOL is the agency that controls the imposition of the IID and the length it is required. You can ask, but the chances of having it removed are slim to none.
Sign up to receive a 3-part series of useful information and legal advice about DUIs.