Chris isn't unemployed. To be unemployed you have to be actively searching for work. Chris is out of the labor force. A bit of a technical point, I guess, but if you see unemployment numbers, it maybe useful to remember they don't count people like Chris.
But Chris is not incredibly remarkable. Stay-at-home spouses are not rare. Neither are people on disability.
While people are correct when they say Chris could work a little without losing the tugboat, the reality is a little more complicated. Basically, he has SSDI because "his autism prevents him from working". If he works a little, the underlying logic gets automatically adjusted to he gets SSDI because "his autism prevents him from working very much". If he earns too much money (more than $810 a month), his tugboat is at risk. Not neccessarily gone for good, but it will go away if he makes that much money repeatedly (9 times over the span of 5 years) and he can only get it reinstated when he stops earning that much money and demonstrates that happened because of autism.
Basically, if Chris works more than 20-25 hours a week at a minimum wage job on any kind of regular basis, he is putting his tugboat at risk. If you take out any moral arguments about receiving benefits, the message is that Chris has to be careful with part time jobs. Suppose he gets a job at Walmart working 20 hours a week at minimum wage. He normally would make $600 to $650 a month, which is great, but what happens if he gets asked to do a couple double shifts?
Which makes his situation not particularly uncommon for people on disability. Also keep in mind that a lot of people, like Chris, don't read the rules that carefully. The actual rules of how much and how often you can work are complicated, so what people absorb is the simpler message "I shouldn't work, because I might lose my SSDI".