Keep in mind that we're looking at this on route-by-route basis, and that's a very oversimplified method. Some trains do/did make turns. The 29 turned to 3 for a few years, and 58 is known to turn into 22, both at Chicago. Sometimes there just isn't a faster turn to make, so equipment has to sit a bit. The 371 is known to catch whatever spare something is laying around. The consists are often switched out and things like 90-day inspections are done at those times.
Overall it may look like 29/30 are laggards but they may be the structural looseness necessary to get a fleet of that size through the shops properly. It's no secret that Amtrak's locomotive utilization rates are very high for the industry, especially off-corridor, so maybe their car utilization is, too.
Also the chart (which is really interesting to look over) might be more useful if the mountainous segments are accounted for. The Rockies, Cascades, Sierras, and Appalachians present an obstacle that will never allow for much over 40-50 tops, which destroys the average. If those segments were accounted for, we could really see where the flat-land ooopsies are happening.
The new Acela: It's not Aveliable.