These articles are indeed often hyperbolic, and many of your points are fine and neglected by proponents. However, "higher bandwidth" probably refers to the n

These articles are indeed often hyperbolic, and many of your points are fine and neglected by proponents. However, "higher bandwidth" probably refers to the number of people per second that can be transported through a certain lane width. At most speeds cars require roughly 2 seconds minimum between them, and they mostly are single occupancy, so they can't do more than 0.5 persons per second per ~12 foot lane. Bicycles can do more on account of less spacing front/back and side to side. (This is sort of surprising given that bikes have a slower top speed, but it's really the time-spacing between vehicles, not their top speed, that matters when you're operating at capacity.) Bus can do more on account of being more passengers per vehicle. Trains are denser yet. All these have drawbacks on other metrics, of course.