I have no idea about the meaning of these flight codes etc. But there is one point (3.30 in the video) where they say 134.2 and then the pilot responds 34.2.
You seem to know about this stuff so is that standard? Guessing it’s not a miscommunication as people would have picked up on it
It’s normal to drop superfluous information to save time and increase clarity of communication. Same with call sign, the full listing would be N72EX (?) but routinely you hear only the last 3.