We need to see how it was setup. A carburetor doesn't care how the fuel is supplied. it can be supplied by gravity for all it cares.
I don't beleive a thing the salesman has texted. Not that he's a liar. He just doesn't know.
Say you remove the electric pump and then discover the mechanical pump actually doesn't even exist?
As
@rumblefish360 posted, a second pump was something that used to be done in some situations. It can be done so as not to interfere with the mechanical pumps operation. I think you'll be better off without both electrically and fuelwise, but without knowing more not recommending a thing just yet.