There are other studies that show we can understand speech at a much higher rate. The critical bandwidth constraint seems to be on stream out, not stream in.
It also doesn't seem to be achievable with on the fly statements, only memorized oration. Notice how my citation interestingly shows that the 39 bits per second isn't a count of syllables, but of semantic information. Some languages have faster, simpler syllables, but the overall information bandwidth flow ends up being the same. You probably can bypass that 39 bit with practice and memorization, essentially applying higher level tags to large bodies of what you're saying via practicing repeated phrases.
That seems to prove where the bandwidth constraint is, on the stream out side.