I believe the point is that older vehicles are exempt from newer rules, regardless of where they are from. Is why I can legally drive my 2000 truck, despite it almost certainly being less than up to current standards.

I think there is a reasonable logic that scrapping the truck would probably be pretty bad for the environment, such that some of the standards are "water under the bridge", as it were. The rest of the logic almost certainly falls on the numbers just not mattering? I don't know.

Besides 25 year limitation, the regulations are a main pain here as it can be difficult to comply with the letter of multiple overlapping regulations, and have the certifications for those. I know headlights end up being a pain for people trying to import cars to the US as all headlights must meet DOT standards. Rinse and repeat with every regulation affecting every part of the car.

What makes you believe otherwise? The parent comment is misleading.