This. A person that gets their work done is not a slacker. I mean when I was in university there was a lad that did nothing, doodled in his notebook, smoked a lot of weed every day. And then aced every exam. He didn't need to appear "busy" to accomplish what he needed in his mind.

Likewise a lot of people work obliquely, letting problems percolate in their subconscious until it comes together and they can put together a solution quickly. These people may drive others crazy with how they work but that is not the profile of a slacker.