Current tenants won’t be priced out because the apartments in question are under rent control. Tenants sometimes want to move, however, but if they do they will lose their below-market-rate rent. So, they instead sublet their apartment to someone else and keep the difference in value. This is a violation of their rental agreements, but if the landlord doesn’t find out they don’t see a problem. Facial recognition and other technologies help landlords identify these tenants who are gaming the system in this way. The tenants gaming the system obviously don’t like that.