How does one position at north east of Tikz rectangle node without offset?

Is there a way to make the top and bottom row come out the same, or is this offset always going to happen?

documentclass[twoside,titlepage,12pt,appendixprefix=true]{scrbook}

usepackage{tikz}
usepackage{pgfplots}
usepackage{pgfmath}

begin{document}
{
    centering
    begin{tikzpicture}
        tikzset{byte/.append style={rectangle,
                draw=black, fill=white,
                minimum width=0.75cm,
                minimum height=1cm,
                anchor=north west,
                align=center, font=scriptsize}}
        tikzset{register/.append style={byte,
                minimum height=0.5cm,
                fill=blue!20}}
        node [byte,minimum height=1cm] (Address Label) at (0,0) {Addr};
        
        node [byte, minimum height=0.5cm, minimum width=6cm] (Register Array 0) at (Address Label.north east) {Register Array 0};
        node [byte, minimum height=0.5cm, minimum width=6cm] (Register Array 1) at ($(Register Array 0.north east) + (0.25cm,0)$) {Register Array 1};
        
        foreach r in {0,1}
        {
            node [byte, minimum height=0.5cm] (Heading Rr D7) at (Register Array r.south west) {D7};
            foreach b in {6,...,0}
            {
                pgfmathtruncatemacro{bp}{b + 1}
                node [byte, minimum height=0.5cm] (Heading Rr Db) at ($(Heading Rr Dbp.north west) + (0.75cm,0)$) {Db};
            }
        }
        foreach r in {0,1}
        {
            node [byte, minimum height=0.5cm] (Heading Rr Da7) at (Heading Rr D7.south west) {D7};
            foreach b in {6,...,0}
            {
                pgfmathtruncatemacro{bp}{b + 1}
                node [byte, minimum height=0.5cm] (Heading Rr Dab) at (Heading Rr Dabp.north east) {Db};
            }
        }
    end{tikzpicture}
}
end{document}

documentclass[twoside,titlepage,12pt,appendixprefix=true]{scrbook}

usepackage{tikz}
usetikzlibrary{matrix, positioning, fit}

begin{document}

    centering
    begin{tikzpicture}[font=scriptsize,
        register/.style={matrix of nodes, font=scriptsize, nodes in empty cells,
            column sep=-pgflinewidth, row sep=-pgflinewidth,
            nodes={anchor=center, draw, minimum height=.5cm, minimum width=8mm},
            row 1/.style={nodes={draw=none}}},
        byte/.style={rectangle, draw, minimum width=.75cm, minimum height=1cm, font=scriptsize},
         ]

        matrix (RA0) [register]{
        &&&&&&&D7&D6&D5&D4&D3&D2&D1&D0D7&D6&D5&D4&D3&D2&D1&D0};
        
        matrix (RA1) [register, right= 3mm of RA0.east]{
        &&&&&&&D7&D6&D5&D4&D3&D2&D1&D0D7&D6&D5&D4&D3&D2&D1&D0};

        node[fit=(RA0-1-1) (RA0-1-8), draw, inner sep=-.5pgflinewidth, label=center:Register Array 0] {};
        node[fit=(RA1-1-1) (RA1-1-8), draw, inner sep=-.5pgflinewidth, label=center:Register Array 1] {};
        
        node [byte, left = -pgflinewidth of RA0-1-1.north west, anchor=north east] (Address Label) {Addr};
        
    end{tikzpicture}

end{document}