The history of advancements in the mile, the marathon, and other competitions seems to suggest that expectations about what's physically possible effect people's performance individually and generally--e.g. apparent endurance barriers.
A similar phenomenon might also exist in the context of longevity. If you get sick and weak at 70 but expect to live to the average age of 90 you might be more optimistic and committed to getting well. If you're sickly at 95 but expected to have already died you might give up the ghost sooner, so to speak.
Assuming that such a phenomenon exists in the context of longevity, I'm intimating that increased awareness about extreme longevity might have the effect of changing expectations and therefore advancing at the margins the extremes of longevity that some people attain. And if the phenomenon behaves like it does in sports, one would expect clustering followed by intermittent breaks to a new limit.
EDIT: To be clear, my main point isn't that this phenomenon exists but that given the possibility of its existence, and in tandem with the clear paucity of reliable, accurate data, the clustering we see might not be strong evidence of a hard barrier at ~117, and in particular not strong evidence that 122 is wildly improbable.