Not sure about this, but I thought if you were adding on a NEW resort (different from you home), you may be eligible for the lower interest rate. We did the tour/presentation last-Sept. at BWV and did not buy at that time (I know, slap my wrist!)...But, we just recently purchased at VWL (original purchase, not add on) and were able to get the lower interest rate. I inquired about it and told that since I had not visited VWL, it was looked at as a NEW visit, etc and made me eligible again for the lower interest rate......
Some of those "non-introductory" rates seem a bit high. As long as you have a good credit rating, you might be able to get a better deal with a credit card or home-equity loan.