I don't know either.
But would bet it is something relatively cheap, yields a rigid glueline, that can be RF cured. Actually, melamine or even urea glues are not all that cheap, but something with a long pot life, spread thin, and when the wood welder cycles, instant. Not something that sets around in the clamps overnight.
smt
West System is pretty expensive compared to the other brands.
If one googles laminating epoxy, you get a ton of other brands.
US Composites is one good alternative to West.
http://www.uscomposites.com/epoxy.html
Predator is made in China now , so I would think they would be dealing with a local brand there.
Pred did have problems with their ferrules for a while when they switched ferrule and glue .
You are right about melamine and poly ure glues. They are not cheap.
The right melamine glue has a great use in one aspect ( at least ) of cue making imo. And I've tested it extensively.
Gorilla is way overpriced and over glorified. There is a better choice imo.
Discovery is fun. Have fun finding it .