who argues that arriving at a different time is actually the same time?

Do I really have to explain that part out loud?

Fine.

Pretend instead of "1 second" it was a tenth of a second. Or a hundredth of a second.

Surely at that point both cars are arriving "at the same time". "same time" is not measured with a laser interferometer. It's about human perception.

So yes, sometimes "different times" are "at the same time"! Especially when you're measuring something with a very vague threshold like "arriving" at an intersection.

In the opposite direction, if it was ten seconds, then it's blatantly obvious that the cars aren't arriving at the same time.

At one second, "same time" and "not the same time" arguments are both plausible, and in the real world I think I'd lean toward treating it as the "same time". But it's not an objective truth either way. One second is in the fuzzy range.