No, you don’t have to make a fleeting note of anything, if you don’t want to or don’t think it’d help you
It sounds like you’re trying to use Obsidian to organize class/lecture notes. When I do things like that (I’m a teacher, but I go to lectures, conferences, etc.), I take handwritten notes in class, which are basically “fleeting notes.” When I get home or to the library, I process them.
So organization in the Zettelkasten method is a bit different. all the notes are going into the same folder so finding them again relies on how well you link them to each other.
parent links are notes that the current note either relies on, or a broader category that the current note is part of. child links are things that rely on the current note.
if you were to do it the way i do, it might look something like this:
you don’t have to do it this way. but this is how i incorporated my study notes into a zettelkasten workflow. one of the keys though, is that you’re writing the note in your own words.