The two issues are somewhat, but not directly related.
Overall, Amtrak still has a shortage of serviceable cars, which has led to the pathetic consists that are smaller than they were 15-20 years ago, and the sellout conditions.
As to the Venture cars specifically, my understanding is that the state of Illinois complained that the Hiawatha was being equipped with new cars before the other IL-supported trains were fully equipped. Keep in mind that because Wisconsin originally ordered Talgos, they weren’t part of the original Midwest consortium order. It was only long after that Wisconsin joined in, so the cars that Wisconsin paid for aren’t technically built/delivered yet. So if Illinois is paying for the cars, they want them on Illinois trains first (I think Michigan was part of the original order, so their trains are okay).