Strong Towns appears to be arguing that the trade-off between movement (roads) and value (streets) is highly non-linear, and that the middle-ground's combined performance is so much worse than either a street or road that it's not worth building. See the comment below about counter-tops vs. stoves for an example of an extreme binary case.
If your goal is to move people, a limited access high speed road is the right way to do it.
If your goal is to support commerce, a low speed, mixed traffic street that can support a lot of homes an businesses in a small area is the right way to do it.
The high speed and land use of stroads makes them inefficient and dangerous for commerce, and the fact that there's so much on-and-off traffic makes them slow and dangerous for transit. They are the worst of both worlds.
Correct. Because as a sibling comment notes, they are a "compromise" that serves neither purpose very well. See the Not Just Bikes video referenced elsewhere in this discussion for a fuller treatment.