Yes, and as you said, it's important to remember that changing the .svg in some way after the work could make the presentation (or the website) unreadable.
Your reasoning is true: in a .docx, .pdf or .odp the pictures are inside the file, so they are standalone and contain all the necessary to be opened and read.
I was searching for a software for presentations, a couple of years ago, when I found Sozi. But as soon as I saw that it led to a final .html, it was natural for me to think at it also as a smart tool to create webpages, publishing online the project after its creation.
I think it could be useful, when one chooses the .svg, to decide if to "Embed the file within the presentation" or "Link the file from its original location". Another possibility is that when one choses the .svg, Sozi makes a copy of it in the same location of the project, and the reference will be, what we say in html, "relative". In this case, the option could sound something like: "Make a copy of the file into the project folder, and open it as a reference".
But if the .svg contains, for example, .jpg pictures, can we chose to keep them external from it and to recall them as external sources, too? I'm not sure, but maybe yes. If so, the project will look as a true website, with a structure and references. I would like it.