I think the problem is that you're assuming that safety rating == safety.
The big deal is to make sure that the companies are able to operate and pass the safety checks with a sufficiently high mark. Since those are based on the existing vehicles, there is no reason to redesign everything to get the same rating at the end.
Your state DOT truck enforcement division very much cares about things like this and it's likely that they've tried to get rules changed or legislation passed on exactly these issues.
Frankly there are much scarier issues to deal with, such as trucks losing their load, tire quality, "running the scales", etc...
It seems the "safety" interpretation here doesn't apply to everyone else not involved.