If you have nothing better to do, hook up say 100 of them in parallel and see if it checks out to about 500M, which would be a more easily measurable value. Or hook up a few of them in parallel and see if they measure as a capacitors I guess. I have a hard time seeing where something like a 50G ohm resistor in such a small package would be useful. Maybe in something that is potted, but then again just the resin would probably contribute a not insignificant stray resistance. So hmm...
Would love to see a "teardown" of it though. Maybe polishing one layer at a time off of it to reveal its internal structure. Maybe send the whole bag, or a carefully selected sample, to mikeselectricstuff?