The message board FAQs include the following: How do I find the most appropriate board for my post?
To select the most appropriate board for your post, think carefully about what information or question you are posting to determine which board would be most relevant. Try to choose the most specific board possible for your post. For instance, if you are posting a query about old county boundaries, post it to the appropriate county board rather than the country or state boards.
...so always look for the locality board that applies...county preferred, Unknown County board only if you don't know the county or there are multiple counties, and the general board only if you don't know anything more specific. But for the locality boards the message should always be more centered on the locality than the individual(s)...since your post was more concerned with the person and the surname and lineage...the surname board was more appropriate.
I think we'd all agree that the boards could use some updating and enhancements both in design and structure.
There is a book you might look at your local genealogical library if you have one near you. Gary Boyd Roberts' Ancestors of American Presidents. It has a pretty good lineage for all Presidents and their families. I have the book and did check it -- and didn't see any indication of a connection...but I'm no expert on Pres. Harrison either so you never know about collateral lines not in the book.