They didn't say vegetative. They said "pretty much a vegetable" fun is a more colloquial term.

From https://paulriddfoundation.org/lessons/iq-table/#%3A%7E%3Atext=Severe+&+Profound+LD+*+Approximate+IQ%2Careas+such+as+mobility%2C+care+and+communication=.

People with a severe learning disability or profound and multiple learning disability (PMLD) will need more care and support with areas such as mobility, care and communication.

And from Wikipedia:

People with Severe ID (IQ 20–34), accounting for 3.5% of persons with ID, or Profound ID (IQ 19 or below), accounting for 1.5% of people with ID, need more intensive support and supervision for their entire lives. They may learn some [activities of daily living], but an intellectual disability is considered severe or profound when individuals are unable to independently care for themselves without ongoing significant assistance from a caregiver throughout adulthood.

I think that could qualify as "pretty much a vegetable", if a bit crass.