

Your safe following distance on gravel at 50mph is more than that. 3 seconds is your minimum following distances on normal surfaces (used to be 2, advice has changed), you should have a 4 second following distance on gravel. https://www.drive-safely.net/safe-following-distance/
China was a really backward country 50 years ago. I expect that China has paved a lot of roads which are still in good shape. Europe by contrast has had paved roads for a long time and those older roads via normal wear and tear are wearing out. The question then becomes when do you patch, recover, or replace - this is in order of both cost and how nice the road is after. Give China a few more decades and their roads will become less smooth because it isn’t worth the cost to make them perfect.