Cracking a Crypto Hard Drive Case
(I bought that model FOR it's antenna figuring it wouldn't hurt, and might help). Adding that plastic antenna got them a marketing and competitive advantage. How many people were, like yourself, sold on the fact that "this adapter has an antenna, so it probably has better range!" and used this 'fact' to make their decision? I wouldn't necessarily consider it fraud, as you never know what internal design iterations the device went through. Maybe the initial design called for an actual antenna and the casing was designed around that. Perhaps later testing showed the antenna provided no actual gain and it was removed, but the cases were already in production. Perhaps a later revision removed the antenna, but the plastic case kept it in order to keep the device recognizable as part of the Freecom brand.
You immediately attribute to malice and fraud that which could be explained plausibly in several other ways. If the device worked as expected, real antenna or not, I fail to see the justification for your complaint. At worst, the design is a smart marketing decision; at best, it is a vestigial part from an earlier design iteration.