Yeah, I've often wished organizations I've worked for would define what an "estimate" is. Do they want an estimate I think there's a 50% chance we'll hit, or do they want an estimate I think there's a 99% chance we'll hit? In my experience they want the 50% estimate and expect us to hit that estimate 99% of the time.

Yes, same thing - and I think we can assume that NASA has people smart enough to know it's the same thing.