Not so much ...as ... usage [duplicate]
Solution 1:
Your initial thoughts seem correct. According to "this version" the wave function does more to describe the 'state of our knowledge' than the 'state of the physical system'.
I have heard this structure used most often to clarify when one might have been led to believe one thing, but something else is, in fact, more likely to be true. As in this variation on an example from Google:
"He kept saying that his novel was unfinished. I believe, however, that it was not so much unfinished as it was unfinishable."