We have two reports. If we're gonna keep trying to solve the puzzle, we have to assume both OPs are posting in good faith, which means either:
-There was a string with edges, or;
-There was a string that OPs recall feeling or looking like it had edges
You can put a metal core in a string made of just about anything and it will make noise through magnetic pickups, so it is certainly conceivable the bass was strung with something not made exclusively of metal.
Questions to ponder
1) What key words might stick out if someone was advertising or marketing a string with edges, or one that felt like it had edges? These will aid us in our search.
2) What properties of a bass string would make it appear or feel like it had edges?
All good presumptions to work from. The most likely answer is some local yokel rigged up what he thought was a genius idea only to go and sell the basses.
As you suggest, a possibility is that one of these oddball strings was actually several lighter gauge strings bound together in some kind of non-glue wrapping. Any glue would make the strings gooey, so if they were wrapped, it was solution/solvent-free.-
One thing to note is that I originally said they sounded thumpy I think was the word. I never once said I plugged the bass in to an amp. People have since added that notion themselves. Strings can sound thumpy, snappy, dull, briight, twangy and all sorts of adjectives without the benefit of an amp. The bass came with an E GHS boomer and three of the weirdos. You can bet they sounded thumpy compared to the metal boomer right next to them.
As to actually amp'ing the thing before changing strings, I have no memory and would have to expect I changed strings immediately on getting back to the dorm and was soon playing the "da-da-da" of "Smoke on the water" that night. That is how a spotty memory of a past event works. I was at the shop with particular people, was home, was playing, there were weird flat strings I got rid of and never heard of again. each of those subsets has associated recollections, the girl who drove but not her type of car though it was blue, what time of day, how long we spent, etc.
Even if I plugged the bass in at the shop I wouldn't have known what I was hearing or be able to even pluck an E properly for my then-inexperienced ear. It would have amounted to a functional sound check at the store.
To my 19yr old eyes the only thing that mattered was Geddy played a Rick and I could afford what was on the wall. It didn't matter what this particular specimen sounded like, as long as it made noise. It could have had razor wire strung on the neck and spikes for pickups and I'd have still gotten it for the Geddy Rick factor