Speaking as a genuine PA Dutchman, no, they aren't all the same. Us Pennsylfanich Deitsch are Deutschmann - i.e. from that place die Englander call Germany. But when the English ear heard Deitsch (dialect of Deutsch), it processed it as Dutch. We are not to be confused with die Hollander!
Around here most patches on wood are referred to as a dutchman, but that plywood stuff we call footballs. A dutchman is designed to cover up a defect or mistake in the wood instead of replacing the whole piece. I don't know that dovetailed bowties would qualify from an historical point of view, since they pretty much call attention to the defect rather than attempt to hide it.
Bill