I've had similar experiences in tracing my own Powhatan Confederacy ancestry.
The Pamunkey gave me a song and dance about being able to trace their surnames back to the 1700's and my ancestor's surname (Taylor) was not one of them. But I have seen a photograph a few weeks ago on the internet of a Pamunkey rez woman with that surname.
The Upper Mattaponi told me to go to the Library of VA;the librarians might be able to help.
The Mattaponi sent me around back to speak to an elder. I won't repeat what she said,but we had a rather cordial talk.
On the Pamunkey website,they indirectly hint that they don't want to be bothered with requests for genealogical information.
As a triracial individual,I was shocked to find out that they (Pamunkey) once had an anti-miscegenation law (1887) slanted against blacks. If one
married other than a white or NDN,one lost the right to live on the rez. But,I haven't faced racial discrimination from modern day Pamunkey,even though I'm brown with kinky hair.
The ancestor that I referenced was my gg grandfather,Allen Taylor,a FB Pamunkey from King William. (Can't completely rule out Mattaponi/Upper
Mattaponi.) He was a mariner and shows up in the 1890 Baltimore City
Directory.(MD)