That is an excellent question that gets to the heart of my critique: what roadblocks are there during construction which means that labor gets deadlocked and waiting for the completion of something else, what learning can be iteratively applied, and is the project decomposable or monolithic?

A solar tower loses on all these fronts. First, the staging of the tower has many different components: leveling of the terrain to accommodate a large structure with airflow (perhaps not needed for the heat collector part, but perhaps?), foundations for the heat collectors, construction of the heat collectors to a sufficient pressure standard that the heated air doesn't leak before hitting the turbine, etc. Then the tower itself is a massive construction project with a large and critical foundation that must be built to exacting standards, then the tower itself, etc.

Utility scale solar has the panel structures, inverters, potentially a battery island, all of which can be built independently. Individual workers can work in a highly parallel manner, learning efficiency that can be translated into their next 1000 iterations of the same task. Further, due to the decomposability of the project, you can build a chunk, learn, and do the next chunk in an entirely new way if there's some innovation (maybe a new mounting process comes to market half way through the build). No specialized labor has to wait for the other part to finish their section, to get more of a specialized part that ran out (since all the parts are standardized and mass produced). There's minimal dependency between the different labor skill sets. And where there is a dependency, between the panel structures and the panel mounting, the needs of the structure are minimal. People are even testing dumping panels directly on to earth, without any structure, these days. If any part of panels are damaged, it has nearly zero impact on the rest of the structure. Whereas with a solar tower, any leak in a section affects a much larger structure.

And the decomposability of solar PV means that it can start operating before the entire thing is built. If money runs out, the fraction that gets built can still generate electricity, until the money can be found to complete the project. You can repower part of the project, add to it easily, scale it in any way you want. It's the difference between a cloud data center and a mainframe.

Thanks, that explains a lot. I hadn't really considered that the giant greenhouse had to be nearly airtight, rather than just directing air towards the chimney, and yes it can't be built piecewise and get a useful smaller version.