Hi Mova,
I have the same boat but 2007.
I have never painted that area, it's not needed since marine growth will not settle there, and as you indicate it also works as an electrical contact area for the anode.
The other area in your picture is definitely corrosion. My sail drive body is completely slick without these corrosion spots.
Are you using the same antifouling coating on the sail drive as on the hull?
That could be the cause - The sail drive is made of aluminum and there are often copper in antifouling for hulls.
You must use an antifouling with no copper in it, I have always used Jotun Aqualine spray can, it works perfectly and one can has now lasted 4 seasons.
And there are never any significant sea growth on my drive.
Hopefully this was helpful :-)