This is something that Brooks had reflected on already in "The Mythical Man Month":

"One occasionally reads newspaper accounts of how two programmers in a remodeled garage have built an important program that surpasses the best efforts of large teams. And every programmer is prepared to believe such tales, for he knows that he could build any program much faster than the 1000 statements/year reported for industrial teams. Why then have not all industrial programming teams been replaced by dedicated garage duos? One must look at what is being produced."

Brooks argues that the coding that happened in the garage is only a fraction of what you need for the final product:

"It costs nine times as much. But it is the truly useful object, the intended product of most system programming efforts."

What we're seeing right now does not feel much different. You can greatly accelerate a first draft, a greenfield project, an experiment, or at least the initial iteration of one. Changing a live production system or a widely used library is an entirely different proposition.