I have been looking through Michigan law and I do not see anything in the law specifically requiring a tether, even on a felony level dui over .10. So your PO may not be telling you the truth about that.
Unfortunately however, parole can change your conditions if, for whatever reason, they feel it's appropriate under the circumstances. To that extent, what parole tells you that you have to do is the law. After all, keeping on their good side is the only thing that will allow you to remain out of prison, and home arrest is, if nothing else, better than that.
You can get hold of your lawyer or retain a new one and appeal this decision to the board. If it's denied, you can have him take it to court
to see whether Parole is abusing their authority by requiring this new condition of you. But that's about all you can do, other than serve the parole as they are ordering you to, because parolees
do not have the rights that people who are not serving a sentence
I'm sorry to be the bearer of bad news.