Interesting. I am also diagnosed with ET (from platelet counts, pathology report noting abnormal platelet morphology, and JAK2 mutation from a marrow biopsy). What made you seek a second opinion?
The first specialist ( hematologist) was referred from local GP. She is a a hematologist, but she wasn't focused on MPNs.
I recommend joining your local MPN alliance to keep up with what's going on in this field. I also recommend finding a specialist with a focus on MPNs. Looks at their papers or listed focus.