Why is the spacing different after a multiline array environment?

Question

My goal is to get equal line spacing between text and array environments. This mostly works without any modification, except for one case: If the array environment consists of more than one line, the spacing thereafter is different.
* There is more space if another array environment follows (cf. column 4), and
* there is slightly less space if text follows (cf. column 5).

I tried to fix it myself (see \fixSpacingAfterMultilineArray), but this alleviates only the case where an array follows, and worsens the problem whenever text follows.

So my questions are:
* Why is the spacing different after a multiline array environment?
* How can I achieve consistent spacing after the array environment, regardless of the content that follows?

MWE code:

\documentclass{article}

\newcommand{\minip}[1]{%
  \noindent%
  \begin{minipage}[t]{1.3cm}#1\end{minipage}%
}

\newcommand{\arr}[1]{
  \setlength{\arraycolsep}{0pt}%
  \begin{array}[t]{l}#1\end{array}%
  % \par\fixSpacingAfterMultilineArray%
}

\newcommand{\fixSpacingAfterMultilineArray}{%
  % array with two lines has a depth of at least 15.60004pt
  \ifdim\prevdepth>15.6pt%
    \vspace{-1pt}%
  \fi%
}

\begin{document}

\minip{ Col1 TEXT TEXT TEXT}
\minip{ Col2 \arr{ ARR1} \arr{ ARR1} \arr{ ARR1}}
\minip{ Col3 \arr{ ARR1} \arr{ ARR1} TEXT }
\minip{ Col4 \arr{ ARR2 \\ ARR2} \arr{ ARR1}}
\minip{ Col5 \arr{ ARR2 \\ ARR2} TEXT}
\minip{ Col6 TEXT TEXT TEXT}

\end{document}

MWE output:

Answer 1

You need to force \baselineskip rather than \lineskip to be used by allowing for the depth of the last row (assumed to be that of \strut)

\documentclass{article}
\usepackage{array}

\newcommand{\minip}[1]{%
  \noindent%
  \begin{minipage}[t]{1.3cm}\raggedright#1\end{minipage}%
}

\newcommand{\arr}[1]{%
  \setlength{\arraycolsep}{0pt}%
  \begin{array}[t]{l}#1\end{array}%
  \par
\vskip-\dp\strutbox
\nointerlineskip\null
}


\begin{document}

\minip{ Col1 TEXT TEXT TEXT}
\minip{ Col2 \arr{ ARR1} \arr{ ARR1} \arr{ ARR1}}
\minip{ Col3 \arr{ ARR1} \arr{ ARR1} TEXT }
\minip{ Col4 \arr{ ARR2 \\ ARR2} \arr{ ARR1}}
\minip{ Col5 \arr{ ARR2 \\ ARR2} TEXT}
\minip{ Col6 TEXT TEXT TEXT}

\end{document}