Note that the terminology in this article is somewhat non-standard. I usually think of a handle as a pointer-to-a-pointer: it adds another level of indirection so that memory allocator can move objects in memory without needing knowledge of all outstanding pointers. IIRC the classic Mac Toolbox (~1990) used them extensively, and that concept seems to be what your Ph.D thesis is about.

The objects discussed in this article would probably be better called "descriptors". They're very much analogous to file descriptors in UNIX: the API returns an integer index into a table, which contains the actual data being referenced. The memory address of the table or its members remains opaque to calling code, and there is no way to access outside the bounds of the table.