Fork down edge style with Tikz 3.0 tree graph

Question

When node/child style is used, it is possible to achieve fork down edge style picured here:

What would be the syntax for the similar edge style, but using graph?

The below MWE produces sloped edges:

\documentclass[10pt,landscape,letterpaper]{article}
\usepackage{tikz}

\usetikzlibrary{graphs, graphdrawing}
\usegdlibrary{trees, layered}

\begin{document}

\begin{tikzpicture}
\graph [
    binary tree layout,
    sibling distance=4mm,
    level distance=8mm,
    components go right top aligned,
    component sep=1pt,
    nodes=draw
]
{
    Supervisor
    -- Current Employee
        -- {
            Subordinate 1--{Worker 01,Worker 02},
            Subordinate 2--{SubSubordinate 21--{Worker 21,Worker 22,Worker 23}
        },
        Subordinate 3-- SubSubordinate01--{Worker 11,Worker 12}
    };
};
\end{tikzpicture}
\end{document}