[ska]

I think you are misunderstanding "missing middle" in a potentially important way, or at least advocates would say that you are - you cast these "missing middle" housing options as a cheaper, inferior option to suburban detached homes. They would argue that that zoning/subsidies/etc. upset that balance and if the field was leveled (e.g. remove zoning blocks from middle density housing, remove subsidies from suburbs) then some?/many?/most? families would choose the more urban, higher density over the SFH in the suburbs.

I'm not sure they are right, but your characterization isn't what they mean.