Surely if it relies on glue to hold it together, it can't be
"self-amalgamating" ?

Of course it can - the glue is solvent or plasticiser loaded
to soften the thin PVC so it cold welds into a solid mass.
The self-amalgamating PVC tape ends up gluing itself in
such a mess that you can't unpeal the roll after a few years.

The rubber etc self-amalgamating stuff you cite is far better.
--
DB.