I have created a table* to show which building types are allowed in which of CodeNEXT's 13 transect zones. The highlighted rows are the "missing middle" types of housing we've heard so much about the last four years. (Click to enlarge.)
The T3 zones are single-family zones, and all "middle" housing is excluded from these zones -- unless one classifies duplexes as "middle" housing. Even then, duplexes are not "missing" from Austin's housing stock, so continuing to allow them is no improvement on the status quo.
The T4 zones are the intermediate zones between the (mostly) single-family zones and the high-density T5 stuff. This is where I expected to see a lot of missing middle.
That is not many Xs. The missing middle is still missing, at least from the middle zones.
This chart actually overstates the amount of by-right middle housing that will be available in T4 zones. Plain vanilla T4Ms does not allow any residential dwellings at all other than live-work units, senior housing, and accessory dwelling units. (It's unclear how one could squeeze ADUs in behind a "main street" type building.) Residential is allowed only in the "open" T4MS sub-zone. The TM4S "closed" sub-zone (my term), in fact, is the only transect zone that does not allow residential by right, a fact that I suspect might give rise to a contentious zoning case or two some day.
*I circulated an earlier version of the table that excluded the "main street" building type from the missing middle. On further reflection, I've decided it should be included since it appears to allow a low-rise (2-3 story) mixed-use building.