In http://geocitiessites.com/heartland/6721/pdump2.htm
there is a letter dated Tue, 23 May 1995 from: Harold Rhode
In it, among other things, he says "there was a Leiba Mendel Pazernov from Vilkomir, Kovna Guberniia the names of whose ancestors and four wives we knew quite well"
In other words, as I understand it, he is saying there was firm family knowledge as to the ancestors of Leiba Mendel Pazernov.
And given that phrasing, it seems clear "they" knew more than just his parents
Leiba Mendel Pazernov is Leiber Mendel Finn
and this profile - Moshe Joseph FinnPazernov - is the great grandfather of Leiba Mendel' = Leiber Mendel Finn
So it seems quite likely the names for Leiber Mendel Finn's parents, some or all his grandparents, and possibly at least one or more of his great grandparents was well known within Harold Rhode's family back in 1995.
So the names of Leiber Mendel Finn's ancestors found on Trees created by Harold Rhode were likely based on family knowledge at least.
Possibly records were found as well, but possibly not.