My rooms (I supervised staff in two rooms) included people with dual-dx (all were profoundly cognitively challenged and most had a secondary mental health dx). The other rooms did not have both dx (just cognitive challenges).
They worked very slowly and often needed a great deal of assistance to do any kind of work. Some of the clients LOVED working. It gave them a sense of pride. Others - well. They didn't. But they had a lot of physical acting out (we had a fair number of aggressive clients).
I'm sure these places have improved over the years and there are more programs for those that don't fit into this model (I did this a very long time ago).
But just to put out there - our 'fastest workers' (and they were not in my room) came nowhere near the independence or productivity of people who were not disabled. Most of them lived in group homes, got full SSI, and used the money they earned as spending money on the weekends.
If those workers DID make minimum wage, I assume it would threaten their SSI.