I mean sure it's cool but I think the point is they've been so consistently spectacularly successful in blowing past mission objectives that it's a bit hard to imagine achieving this wasn't the "expected result" (maybe we can cut a bit of slack for Pathfinder/Sojourner which was the first complex mission after the Climate Orbiter debacle and over-delivered only 12x).
The issue here is that there's a mismatch between the probability distribution and result. In reality, either the equipment will fail some time on entry/initialization and won't be able to complete any missions, or it will work for one and thus probably work for a hundred of them.
If you promise one run and fail to complete it, it's a disappointment, but eh, it was a high-risk mission anyway. If you promise a hundred runs and fail to complete even one, you'll catch a ton of flak. If you promise one and complete a hundred, you're a hero.
The math checks out that way, especially when one single mission is good enough to get the funding anyway. Everything else is literally a bonus, why promise ten when they're paying you for one?
Yes - there's clearly an incentive misalignment in setting & communicating realistic mission risks & expectations which is not too surprising given the politics behind how NASA is funded.
What happens over a period of time in any organization if you consistently under-commit & over-deliver is that people stop believing in your "official" under-committed number ("It's just on-paper") and start creating their own informal "realistic" expectations (which are possibly different across stake-holders) and start taking (possibly mis-aligned) decisions based on these. As you may imagine, such situations tend to blow up from time to time.
