It isn’t a universal thing, but yeah.

As others have said, a tablet typically refers to a prebound pad of paper, and most typically to one that is bound across the top, ala legal pads.

Like anything language related, usages bleed and shift. Back before bound paper was a thing, it was used to refer to any flat writing surface.

It goes back to tabula, from Latin, where the primary (but not only!) use was for the equivalent of a placard or other inscribed label, as well as any writing surface.

Think like a writing slate. The term tabula rasa is essentially the same as “clean slate”, and refers to writing on an actual slate being erased.

So, tablet over time has been used for pretty much any writing surface at all, and it’s not unusual to see it applied to any bound writing surface, even if it’s a loose-leaf binder. It is archaic though, and wasn’t exactly common in that specific usage (not that I’ve ever heard or seen anyway). But I have seen and heard it used that way, particularly for the kind of binders that run across an entire edge of a stack of papers, like you might use for a presentation. For ringed binders, I’ve only heard it used a handful of times, and never seen it in print.

Caveat: I’m just a word nerd, so I’ve never tracked things down to primary sources. Etymology is a fairly rigorous thing, and nothing I’ve said here is exactly rigorous. Take it as a casual thing pulled from memory rather than something you could cite in a class assignment.