Interesting, but really of no practical value except for "See it can be done"
This isn't going to allow for any type of realistic FTL Communications, because the only way they did it was to change the medium of the glass jar. You can't change the medium of interstellar, or even interplanetary space.
Although 300 times the speed of light is nothing to sneeze at. If we COULD duplicate that in real space, that would mean we could send a one way transmission to Alpha C in just over 5 days.