pgfplotstable: Keine Wirkung von typeset cell/.code

% every row no 0/.style={ % Kein Effekt
%every nth row={1}{ % error
%every last row/.style={ % Kein Effekt
every head row/.style={ % geht
typeset cell/.code={%% 
\ifnum\pgfplotstablecol=\pgfplotstablecols%
\pgfkeyssetvalue{/pgfplots/table/@cell content}{Letzte: ##1\\}%
\else%
\pgfkeyssetvalue{/pgfplots/table/@cell content}{Sonst: ##1 &}%
\fi%
}%%
},

\documentclass[margin=5pt,]{standalone}
%\documentclass{article}
\usepackage{pgfplotstable,multirow,booktabs, filecontents}
\pgfplotsset{compat=1.16} %<-- command `every column'

\begin{filecontents*}{\jobname-data.csv}
A,B,C,D
string1, string2, string3, string4
string1, string2, string3, string4
string1, string2, string3, string4
string1, string2, string3, string4
\end{filecontents*}

\pgfplotstableset{
% every row no 0/.style={ % Kein Effekt
%every nth row={1}{ % error
%every last row/.style={ % Kein Effekt
every head row/.style={ % geht
typeset cell/.code={%% 
\ifnum\pgfplotstablecol=\pgfplotstablecols%
\pgfkeyssetvalue{/pgfplots/table/@cell content}{Letzte: ##1\\}%
\else%
\pgfkeyssetvalue{/pgfplots/table/@cell content}{Sonst: ##1 &}%
\fi%
}%%
},
}

\begin{document}
\pgfplotstabletypeset[string type, col sep = comma]{\jobname-data.csv}
\end{document}