The vehicles use a monorail, not asphalt. Both in the concept video and the actual prototype of the electric sled in a tube video.
Also, the concept video shows multi-user pods. If you pack them as full as a rush hour subway, you could probably equal or exceed a subway's throughput.
I think 300 ft is for 75 mph. Using https://en.wikipedia.org/wiki/Braking_distance, the distance at 125 mph is 55 m/s * 55 m/s / (2 * 1 * 10 m/s2) = 150 m = 500 ft, resulting in 2 people * 125 mph / 0.09 mi = 2.8 khumans/h.
(On the demo video, their vehicles look like they are tire-on-asphalt.)
Also, subways have a typical capacity closer to 30 khumans/h in dense urban areas (https://www.thoughtco.com/passenger-capacity-of-transit-2798...).