Uneven vertical space with enumerate and multicols

#enumeratebabel-frenchmulticolspacingvertical-spacing

I'm having a vertical spacing glitch in this minimal example:

\documentclass[11pt,twoside]{book}
\usepackage[T1]{fontenc}
\usepackage[french]{babel}
\usepackage{microtype,textcomp}
\usepackage[total={6.25in,10in},left=1.25in,top=0.5in,includehead,includefoot]{geometry}
\usepackage{enumitem}
\usepackage{tabularx}
\usepackage{multicol}

\begin{document}

\begin{enumerate}
    \item %Blabla
        \begin{multicols}{2}
        \begin{enumerate}[label=\alph*),itemsep=11pt]
            \item This is a simple test.
            \item This is a simple test.
        \end{enumerate}
        \end{multicols}
    \smallskip % Without this command, the spacing is too small!
    \item %Blabla
        \begin{multicols}{2}
        \begin{enumerate}[label=\alph*),itemsep=11pt]
            \item This is a simple test.
            \item This is a simple test.
        \end{enumerate}
        \end{multicols}
    \smallskip
    \item Blabla bla blabla bla bla bla blabla.
\end{enumerate}

\end{document}

Preview of what this code is doing, and the glitch shown in red:
enter image description here

The space indicated in red is too big, compared to the green one. It's uneven and I don't understand why. If I remove the \smallskip command, it's then too small. If I remove the babel package (which I don't want to do!), then the issue is solved.

So what am I doing wrong here? How can I fix this issue, while keeping the french babel command?

Note that I need to keep the multicols environments inside the enumerate. The full document has lots of them.

Best Answer

babel-french customizes vertical spacing in lists (i.e. \itemsep, \parsep, \partopsep, \topsep) when French is the main language, but provides an option \frenchsetup{StandardListSpacing} to revert to the standard settings.

In this example, enumitem is loaded. It enables a far better control on lists than babel-french, so I strongly recommend to use option StandardListSpacing and let enumitem alone customize lists.

The glitch mentioned vanishes with \frenchsetup{StandardListSpacing}. Actually, the vertical space above item 3 is reduced by babel-french (without this option) which looks wrong, the one between items 1 and 2 is unchanged.

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