Hi. I have something like this with SX900; I agree that it's most likely how the sample was recorded.
As a matter of fact little flaws like this reveal that we listen to the same sample over and over again, and we do the same when samples are "perfect", which is why we can get tired of it.
Inperfections, flaws - they can make it to sound more natural altogether, but it this case it would help if we had a variety of samples for a each note, so that it wouldn't be so repetitive.
At least with Genos it's easier to add variety with styles and other sounds. Imagine having a digital piano with few sounds and absolutely nothing to add to them.