unable or too lazy to understand the clock,

They can understand the clock? Just not the analog clock. Why should they anyways? It's not like that's the only way to tell time and since reading analog clocks is an unrelated skill why do u think they're not fit to write exams? It has nothing to do with IQ, it's just that analog clocks aren't as common as they used to be. Hence, they're less used to them than previous generations. They probably can learn to read them if they wanted to, but they just don't bother, since they don't really need it these days

who are too lazy or too stupid

They do know how to read the clock (digital ones :) ) Again, it doesn't make them idiots or lazy for not learning something they don't really need to learn

Intelligence is an ability to obtain knowledge and skills. If someone lacks both, it is a strong indication of them not having enough intelligence to obtain them.

What makes you think they don't have the ability to learn how to read analog clocks just because they don't? You might not know how ride a horse, but that doesn't mean you can't learn how to. Are you an idiot for not learning how to?

Why are you so adamant that reading an analog clock is required to pass an exam that doesn't feature any material related to reading analog clocks?

Except, they do know how to use a clock. Just not your favorite clock