Everyone's time in an exam, is limited. Skimming though to get a gist of a question and decide the order you want to tackle them (those areas you're more confident about do first, then pick up extra points on less confident areas after) is fine. But once starting on a question in earnest the time used to understand it properly is time invested, not wasted. You need to judge the amount of attention needed, but that's what practice questions are for.
As an analogy consider a wild west gunfight at high noon. Who comes out best, the one desperate to be fastest, fumbles with their gun, fires wildly in the general direction and hits nothing relevant, or the one that draws quickly, but not so much so that they lose control, takes time to aim properly, then squeezes the trigger ?
Know what is important and needs time otherwise you'll shoot at the wrong answer.