There are some exceptions to the rules/law.
They are based on the age of the vessel.
I own two old boats without titles.
One is a 81′ Lund that was originally owned by the Minneapolis park system that was never titled, there is a check box on the registration sticker that states non-titled.
The second boat is an 11′ 1971, Weere paddle boat. The length requires registration but there is no hull identifier.
Where are you located, try a different register office. Some are more helpful than others.