The very last line in this documentary says it all:
"... which will decide whether the varying speed of light theory is pure nonsense or not."
While interesting, this is a documentary about theory. As such, it may hold historic interest... but will hold little interest for the average person. Even though they obviously try to "dumb it down", the truth is that much here is pure conjecture... and is presented in such a jumbled high-sounding manner that by the end, anyone not a mathematician may need to go for the aspirin bottle.
What we have here are high-level scientists discussing pure theory, much of which contradicts other scientists with opposing pure theory, none of which is actually proved. That's totally okay of course; diversity is the spice of life. It is often the case that the truth lies somewhere in the middle of diverse thought.
There are interesting things to be learned here, but it is shot at the audience with such a shotgun pattern that little of it is likely to hit the target. Okay, the universe is accelerating. That's pretty fascinating. Next step: let's totally guess at why, create imaginary "constants" that seem to explain things, and then without factual data present that information to an audience to which none of this really matters. Thus back to the original quote. None of this is actually proved, and could turn out to be science or claptrap. That's the ultimate message that came across to me... and I usually tend to like this kind of thing.
If anyone is hoping to learn something from this or gain any insight into Einstein (other than the fact that he was an incredible genius), the viewer is likely to be disappointed. The only thing I took away from this was about 60 seconds of screen time: that light measured from quasars billions of years old is different from light measured from younger quasars... hinting that the speed if light is not constant. Of course there are other variables that could explain such, so... even that had its questionable value.
This is a documentary about scientific opinion, no more valid that string theory or the (now highly questioned) "big bang" itself. This is somewhat like dropping a rock in a deep hole and never hearing it hit bottom. Why is that? One could conjecture and theorize all day long and still not know the actual reason why one never heard the rock hit. It's posturing and nothing more.
Thus the primary problem. In effect this throws out a whole bunch of "maybes" without really providing any substance... and does so in a manner so scattershot the average television viewer is going to either shut it off early, or leave the end scratching their heads, themselves wondering like that scientists, whether any of this has basis in reality... or is absolute nonsense.