Welcome to Connect, @qbf This is one of those situations where it’s not good to speculate. PV (primary or secondary) or any blood condition can take some sleuthing to pinpoint the diagnosis. There can be several causes for elevated hemoglobin so your doctor is trying to rule out the most likely suspects before confirming the diagnosis.

The first step is generally testing for any genetic changes such as JAK2 mutation which can cause the overproduction of blood cells. Your test was negative for involvement which is good. So your doctor will look for an underlying condition. When the body senses a lack of oxygen it calls for the production of more red blood cells to increase the oxygen supply. This can be as simple as living in a higher altitude or having sleep apnea. But there are also a number of other health conditions which as heart, lung or kidney issues that can cause secondary PV.
From information I’ve read however, secondary PV generally has a high red blood count along with high EPO. Primary PV has a high red count and low EPO. Your EPO is very low from your results.

If you haven’t read these yet, here are two good articles with information about both PV and Secondary PV.
https://www.healthline.com/health/polycythemia-vera#diagnosis
https://www.healthline.com/health/secondary-polycythemia
Because changes in the bone marrow can also bring about conditions like polycythemia vera, at some point if there are no firm answers, it would not be a bad idea to push for a bone marrow biopsy. It gets a sample of tissue directly from the manufacturing site for your blood and can give your doctor a much better picture of your overall marrow health and its ability to produce healthy blood products.

Has your doctor discussed the next step to take? Do you have any symptoms associated with your high hgb?