I would say that I fall more into that category than the typical "acting out" BPD. At least now. I did have some problems with acting out in my youth, but they weren't totally uncontrolled and I mostly turned everything inside even then.
I see the quiet BPD as just being a different manifestation of symptoms, and a different manifestation of the same internal experience...it just tends to be overlooked more often because it doesn't appear in the way one would expect. I get the sense that a lot of the "acting out" behaviours of classic BPD are actually red herrings, in the sense that they distract from the real issue which is the internal, mental, emotional experience of having BPD.