In my experience, this fact was the #1 reason why some peers dropped out of PhD programs. They joined expecting a continuation of undergraduate education, which consists largely of recapitulating what appears in the secondary literature. Instead, what they got in graduate school was the expectation that they would be producing the primary literature. That's a very different game.
It was a game these peers discovered they hated playing. Nothing in college can prepare you for the isolation of spending your time becoming the world's expert on a narrow technical topic. Your usual reinforcement mechanisms of approval from family and friends gives way to slight comprehension at best. Then there is all of the alone time doing research requires. But I suspect the hardest part of all is the seemingly endless lineup of dead ends and false hope. Not only is success not assured, you often have no idea whether the result will have any utility even if you succeed.
Then, just when you've gotten the hang of this finding answers game you discover that the real expectation is to be the one who formulates good questions. The kinds of questions that, although they will certainly involve dead ends, will ultimately pay off in some meaningful way. Very little in a bachelor's prepares you for doing this. It's a hard-won skill that comes from a round or two (or three or four) of months (or years) spent answering questions that nobody cares about. A lot hinges on your relationship with your advisor on this one.
The PhD isn't just a bachelors degree but harder. It's a completely different animal. The skills in this article are very useful toward that end. But there's a lot more to the story when it comes to skills for finding answers to those unanswered questions, and formulating worthwhile questions without answers.
The benefit of all of this work and discomfort is that you come away with the ability to answer worthwhile questions that haven't yet been answered. And that's a highly transferrable and applicable skill.