Welcome to Sclero Forums! I'm sorry you have scleroderma and need to apply for disability.
Generally speaking, the answer to this question would be "Yes." See Systemic Sclerosis Prognosis and Mortality. And if you have severe systemic sclerosis, your case will be fast tracked by Social Security. See Disability and Scleroderma by NOLO.
That said, many of our members initially received disability based on other diagnoses, such as fibromyalgia, often because of the extreme lag between onset of scleroderma symptoms and diagnosis.
If you are doubting your doctor has you properly categorized, based on information on our site, then you are probably right. You might want to make sure that they are a listed scleroderma expert, and/or seek a second opinion. Most usual rheumatologists have extremely limited experience with scleroderma and thus commonly get the diagnosis or treatment wrong.
So to optimize your care and longevity, you want to make sure you have a scleroderma expert on your medical team. If you have to travel to see one, they are typically outstanding at working with your local rheumatologist or doctors to continue to monitor your care. Also see: Types of Systemic Sclerosis.