Is multivocality really hypertext?

As I read through George Landlow's "Hypertext and Critical Theory," I have come to see that there are multiple sides to hypertext that give different arguments to critical theory. One that stuck out to me was hypertext and multivocality, because I never really saw multivocality as a hypertext; if anything, I thought of it more as heteroglossia. I usually think of hypertext as different types of text in a piece (pictures, images, words, interactive interfaces, etc.) rather than different texts in a text. On page 36 with Bakhtin's description of the "polyphonic literary form of the Dostoevskian novel as a hypertextual fiction in which the individual voices take the form of the lexias," this validates the point that this would make it hypertextual. I, on the other hand, saw something like Public Secrets as hypertextual because you actually have the different voices in addition to text, images, sounds, and interactivity.

The one thing that I wonder is if these are actual different voices of different people in the Dostoevskian novel? Or are they different voices made up by the author? I think this greatly makes a difference, because if it is one author with multiple voices, it is simply multivocality, not hypertext since it really is one text from one author. However, if it is multiple voices from multiple people that come together for a book, I would consider that more hypertextual.