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.
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.