Is this a situation where all the world's skateboards are made by a handful of companies, with labels slapped on?

yes in essence. the best is canadian maple and you really only want to pick brands that use it. you also gotta sort brands by skater owned. if they are "skater operated" it means theyre owned by some big company and you bet cheap wood is being used. its like in golf where the cluibheads are arbitrary and youre really just buying the shaft. skateboard companys are really in the truck and axle and wheel business which separates them.