Having not kept up on this topic, after a little research it looks like this very affordability and income cutoff was a big topic of discussion in 2018:
https://www.modeldmedia.com/features...ce-030318.aspx
https://www.bridgedetroit.com/how-re...dable-housing/
It's pretty clear that the higher end units will be subsidizing the affordable units in the Exchange since the AMI for Detroit residents themselves is much lower than for the region and it's unlikely that they'll fill up the 31 units with folks right at the 80% AMI limit. It will have people between 50-80%.