I'm not sure if I would completely agree with your assertion that their relationship is static. If anything it would seem that they are drifting apart as a result of Naruto's lack of desire or ability to fulfill a desire that Anko wishes to explore. This would imply to me that Anko's desires have evolved from when she first joined the Harem.
To me right now they are at that uncomfortable place where both parties know there is a problem between them but are unsure on how to approach it.
To your last point about him being too forthcoming. What you say is true, but at the same time while I can see Naruto not talking about his relationships, when asked by those he considers friends I can't see him outright lying to them.