I cannot play video on my computer, so I cannot see your link. All the doctors who confirmed Terri's PVS status and her cortical damage not only saw the parents' "videos" but examined her in person. She had been in a PVS condition for 15 years.
The following is excerpted from Bradley et al.'s Neurology in Clinical Practice (Butterworth-Heinemann, 2003):
“In the persistent vegetative state, patients have lost cognitive neurological function but retain vegetative or noncognitive neurological function such as cardiac action, respiration, and maintenance of blood pressure… This state follows coma and is characterized by the absence of cognitive function or awareness of the environment, despite a preserved sleep-wake cycle. Spontaneous movements may occur and the eyes may open in response to external stimuli, but the patient does not speak or obey commands.