It was just my humble assumption (no "statement" as you put it), since as far as I know the "humanization"-Feature was introduced with the Dimensions-Serie where recordings of the single players of an ensemble constitute the sound ot the whole ensemble and in this context it seems to me at least from its Idea most plausible, since the small detuned abberations of the humanization-feature makes (as far as I understood) sens as far they provide that always changing small detune-effecxts you hear only you in the ensemble which is playing the same note but for small individual intonation-differences produce those phaseshifting effects we associate with orchestral section-sounds.
For solo-instruments there is as I understand it no reason to produce those differences since the natural human attack is already recorded with the violinist who plays the tones who makes our patches. The problems only began if you double this soloist and get exactly the same human abberations twice when you let play the same note with the same patch simultaneaously, which would not produce the wanted ensemble phaseshift As far as I understood the traditional way to avoid any machine-effects for single instruments is round robin. So even if the smart orchestra includes Solo-patches, it still does not include dimension-series-instruments and does not have that much need for dimension-series features.
Nevertheless I would wellcome to have the dimension strings in Synchron-Player and if they would ever do so, I expect they will also introduce the humanisation-feature to. But that is of course all just my personal guess and only one point of view among others which one might contribute to this discussion here.
And I am sure the people of VSL are much more able to give you the reason, why neither the percussion, nor the piano, the section-strings nor the smart-orchestra seemed to make it necessary for them to introduce this feature. I at least strongly believe, that if they would have had any good reason to do so, they would have done already. But if you think they dont, feel free to 'teach' them what you think you know better than the VSL-Developpers.