Certainly some bias I would think. For me personally though as someone who had some form of ADHD as a youngster, I was taken out of the regular classroom in grade 4 and put into a special ed class for part of the year which ended up being excellent for me in the long run, I did find this interesting from the article:
"There was certainly a high proportion (9%) of patients across the whole cohort of 288 who had a comorbid neurodevelopmental disorder (ADHD, ASD or intellectual impairment). This is a higher rate than in the general Australian population, where rates of ASD are 0.7% and intellectual disability 3%"
That being said, I also have now a symptom known as motor impersistence, inability to protrude the tongue or keep eyes closed or make a tight fist for 10 seconds (I can barely do this for more than a second or two and could be why sometimes I can't pick things up and hold them) which is seen in ADHD individuals but also widely in Huntington's disease patients and also stroke, schizophrenia and TBI patients. When I try and do these things like keep a tight fist, I have facial grimacing and as well if I extend my arms in front of my body most often they start going all over the place although sometimes they do this all on their own. At any rate, it's interesting is the neurodevelopmental aspect the authors talk of which has also been looked at in Huntington's disease patients ie
Perinatal insults and neurodevelopmental disorders may impact Huntington's disease age of diagnosis
"In the neurodevelopmental disorders ADHD had the largest effect, but the effect of individual insults on the overall hazard ratio was small. ADHD may mimic the earliest symptoms of HD, and thus we only included cases where ADHD was reported before 20 years. This was well before the average age of diagnosis of 47 years in the neurodevelopmental disorders group, and presumably the ADHD in these cases represented the neurodevelopmental disorder and not an early manifestation of HD. The association with neurodevelopmental disorders was not replicated in the Enroll-HD cohort, likely due to insufficient sample size and divergent participant characteristics. Despite these limitations, here we provide the first clinical association of early-life events with HD age of diagnosis."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6226577/
Huntington's Disease in a Patient Misdiagnosed as Conversion Disorder
"Neuropsychiatric disorders often have overlapping and ambiguous presentations, constituting a diagnostic challenge. These could be more noticeable in individuals with LoHD, in which cognitive impairment, rather than chorea, may be the major source of disability.
Thereby, this case enhances the importance of effective collaboration between medical specialties that are dedicated to the study of the brain. The diagnosis of HD was finally achieved, only after the involvement of NT, showing that a multidisciplinary approach is a key factor in this kind of cases.
This case report also alerts clinicians for the need of a careful investigation of motor abnormalities in psychiatric patients, before attributing these symptoms to causes, such as iatrogenic effects or Conversion Disorder."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835269/
Also of potential interest:
Motor and Somatosensory Conversion Disorder: A Functional Unawareness Syndrome?
"The neglect syndrome is defined as a right-brain/left-body unawareness disorder characterized by impaired ability to report, respond, or orient to novel or salient stimuli; it is associated with right-hemispheric lesions.
36,
37 Subtypes include sensory (somatosensory, visual, auditory), motor, hemispatial, and personal neglect.
38 Of particular interest is motor neglect, characterized by impaired motor intention generation and exemplified by limb underuse, hypokinesia, and inability to sustain motor movements (motor impersistence), despite the absence of corticospinal system damage.
38,
39 Notably, functional weakness resembles motor neglect. Structural studies in motor-neglect stroke patients identify a pattern of right hemisphere-predominant frontal, parietal, striatal and thalamic lesions,
40–
44 and implicate cortico-cortical (frontal-parietal) and cortico-subcortical pathways in lesional motor neglect."
https://neuro.psychiatryonline.org/doi/10.1176/appi.neuropsych.11050110