Hello David,
I have already answered to your mail to our support team.
Una Corda is an interesting option in the hands of a profesisonal piano-tuner - you can manipulate many parameters here, and adjust it to each player's preference.
We have decided to emulate the effect internally, without too much interaction with the original sound, to offer this rather rarely-used option for everyone interested - without doubling both our recording and editing efforts and also the sheer data size of the already huge piano.
I'm sure that you understand this decision, the feedback we have received over the last 5 years (since the first Synchron Piano, the Yamaha CFX) indicated that pianists out there are happy with the current solution.
As you have probably already seen, our software is a subject of continuous improvement - let's see what else we can come up with. There's always room for improvement!
Best,
Paul
Paul Kopf Product Manager VSL