My ex-T used to greet me in a similar way. I saw her at her home, she would open her front door to me and she wouldn't say anything or look at me. When we sat down she didn't say anything until I spoke. I asked her why she did this. She told me that it was because she didn't know what feelings I would be coming with. I think she meant that she was being a blank slate and did not want to impose her own mood or feelings onto me. I accepted it at the time. My new T usually says 'how are you' when we sit down and it feels a really caring question in contrast to my ex-T, I never tire of hearing her ask it, as I feel that she genuinely wants to know. I think I feel similar to you that I don't like it when a T doesn't greet you, but I don't think that it necessarily means your T is ignorant or dismissive. You say that she changed her way of saying goodbye after you discussed it, maybe if you discuss the greeting that might also be helpful?