I work in law enforcement and am very familiar with DUI case law. You are correct. Refusing breath can still put you in the highest tier, but blood will not. If you refuse a search warrant for blood, then the grading does get bumped up again.

Here is a good grading chart that appears to be up to date: https://www.mcandrewslegal.com/wp-content/uploads/2022/10/dui-penalties-in-2022-version-2.jpeg