Since they're very up front about referring to them as Accessory Dwelling units, the primary market is likely people who want to quickly put an ADU in place alongside a traditional single-family home for extra living space or rental income.
About one-third of the cost of new multifamily development is typically tied up in zoning/permitting/planning processes. Against that backdrop, ADUs -- particularly if the city pre-approves designs, which seems like something this product would be ideal for -- are a growing part of housing inventory and housing affordability in many cities.