Exactly correct. If it's not their smartphone of choice, it'll be doodling in the notebook, playing word games on paper with their neighbor, doing the sudoku or crossword puzzle, or some other distraction of their choice.
Speaking personally, I had a laptop on which I took notes for my classes during my first semester of college, and I was faithful about doing so. I was required to take an intro PoliSci course, however, and just couldn't give two licks about the material, so I was constantly playing various games on my old Titanium PowerBook G4 (mostly Escape Velocity; Nova and Super Mario 64 via emulation) whenever the professor started going off on tangents. I'd still come out with almost a page of notes by the end of each lecture, but I was definitely distracted in that class (I was good about staying focused in the others, however).
What I didn't realize was how much I was distracting others. We had assigned seats for the exams in that class (400+ students in the class), and when the first exam came up, I sat down in my assigned seat next to a guy I had never met before. He took one look at me and asked me why I stopped playing "that space game" since it was a lot more fun to watch than Super Mario 64. Turns out that even though I was sitting on the aisle about halfway back in the class, over a 100 students could probably still see my laptop and were being distracted on a regular basis.
In a moment of cosmic irony, that first semester went VERY poorly for me...in the classes that I actually focused in and studied. My best grade of the semester actually came from that PoliSci course that I could've cared less about.
On the flip side of things, I eventually did develop a healthy respect for the attention of others and made a point of trying my best not to distract other students. I even went so far in several classes as to simply turn on a text editor, turn off the screen, and touch type for the entire class with the screen closed part of the way. Again, however, in an additional odd twist of irony, my touch typing ended up being a distraction for several students sitting behind me who thought I was just goofing off and playing at taking notes, wondering why I kept up the charade for the semester. Apparently the students in that Intro to Architecture class (that's architecture of the Greek and Roman variety, not the computer variety, mind you) hadn't seen someone who actually knew how to touch type before.