> The number of public universities is in the 3-4% range.

The National Center for Education Statistics disagrees with 3-4%.

  In 2019–20, some 21 percent of undergraduates and 11 percent of 
  postbaccalaureate students reported having a disability. . .

That's a different statistic. Not all students who report having a disability on a survey will be registered with their school's disability office.