On its face its a really weird policy to have but if you think of it, hiring people with disabilities preferentially is just good business for the government.
An able-bodied person and a disabled person have the exact same needs but the able-bodied has probably over twice the opportunities to find gainful employment. The disabled person can end up on the unemployment, long-term disability and live in poverty which brings along a plethora of health-care and social welfare considerations or they can be given that entry level job and save the gov a shit ton of money on all the other line items.
For someone with a significant disability, finding a stable public sector job that does a reasonably decent job is an incredible sense of security. Even at that it can be a constant challenge of dealing with managers not understanding or questioning their limitations, and piling more stress on because even though they can do their whole job, it might not look the same as everyone else- modified hours, breaks, more remote work, etc someone finding a job where their disability can be managed is absolutely going to be more likely to stick with and work hard for an employer that gives them a shot and treats them decently. For jobs that mostly involve using one’s brain, it can be frustrating to have currently or prospective employers who are unable to look past whatever disability they either visibly see, or are told is there. For a lot of people with disabilities, finding a job that will recognize their capabilities and employ them up to them can be incredibly difficult.