You are wrong. 18-20 year olds should not drive such large trucks. They lack the experience and driving skills. There is a lot of situational experience needed. If you think going across a state line is arbitrary, it may be, but it is also putting younger, more inexperienced drivers into unfamiliar situations where they can be overwhelmed, and not have those valuable skills that experiences provides. And, I guarantee you that insurers are not excited about younger drivers obtaining CDLs.
I have posted on this subject before, and it's Team Red that's making it political. It is simply a bad idea, and I have said so on multiple occasions. This is the wrong solution to the problem. Making driving better for current drivers would help in recruitment and retainment, and allowing more foreign born drivers is the answer.