I think there's something to be said for choosing an obvious and informative name such as "Project Stream" over a flashier but non-intuitive name.
Also, at least for now it really isn't a finished product. Perhaps they'll re-brand if the test pans out and they actually start selling a service, or maybe they'll just keep the moniker like Project Fi has.
The gap between a "test" and a product is huge. I don't think it's wise to dump resources into building a product based on unproven technology.