The problem when dealing with any company that has proven itself untrustworthy is that by default the innocent "plausible" option is probably no longer the "likely" one.
And I say this knowing that intentionally deleting data is harder than it looks.
Something about game theory, art of war, and the difference between stated intentions and actual intentions.
Trustworthiness comes from alignment of stated intentions, actual intentions, abilities and actions. Someon can have integrity between stated and actual intentions, but fail to follow through. In this case I think we doubt the integrity between openais stated and actual intentions.
So Sam can be saying stuff and then we find out he wasn't being honest. We can learn over time about his intentions by watching actions instead of listening to what he says. Then we can make new assumptions based on what his actual intentions seem like.
Based on what I assume Sam's intentions to be (with some healthy suspicion of the alignment between his stated intentions and actual intentions), I'm still skeptical that the reason for the 30 day thing goes far beyond quality control, the difficulty of balancing deletion and redundancy and the features of the tech stack they are using.