Well considering many are DX'd with bipolar when they are bpd, this is not unbelievable that they think you are BP. What they have done is a good analysis. They've been realistic in saying they wouldn't DX you with bpd until after a year and that makes sense. There are some things with BPD that could only show up with longer term patterns of behavior. I think this is a good thing they want to wait to see.

My suggestion is that you have a good set of clinicians for your therapy and you should stick with it. More than likely if you are truly bpd they will see that. Give it time and after getting to know you and your behaviors they will more accurately be able to DX you.

Thing also to keep in mind is that many of the meds if they put you on any are good for both BP and BPD so you'll still be in good care for now.