Nobody is claiming that.
After 25 years, it is assumed to be so safe they don't even need to comply with vehicle safety laws. If the import ban was about safety, it wouldn't ever allow cars previously legally considered 'unsafe' onto the roads, but the 25 year law pretty much gives away it was about people importing Lexuses and BMWs for less than it cost to buy one in the US, which made the manufacturers unhappy.
1: https://www.nhtsa.gov/importing-vehicle/importation-and-cert...
I suspect the 25-year cutoff is mostly about allowing enthusiasts to drive classic cars. There's a small number of them. Allowing millions of new unsafe cars to be sold to random consumers would be a terrible idea. I think the rules make sense.