Difference between tableofcontents and listoffigures internal codes

Question

In standard classes book.cls and report.cls we find

\newcommand\tableofcontents{%
    \if@twocolumn
      \@restonecoltrue\onecolumn
    \else
      \@restonecolfalse
    \fi
    \chapter*{\contentsname
        \@mkboth{%
           \MakeUppercase\contentsname}{\MakeUppercase\contentsname}}%
    \@starttoc{toc}%
    \if@restonecol\twocolumn\fi
    }

and

\newcommand\listoffigures{%
    \if@twocolumn
      \@restonecoltrue\onecolumn
    \else
      \@restonecolfalse
    \fi
    \chapter*{\listfigurename}%
      \@mkboth{\MakeUppercase\listfigurename}%
              {\MakeUppercase\listfigurename}%
    \@starttoc{lof}%
    \if@restonecol\twocolumn\fi
    }

In article.cls

\newcommand\tableofcontents{%
    \section*{\contentsname
        \@mkboth{%
           \MakeUppercase\contentsname}{\MakeUppercase\contentsname}}%
    \@starttoc{toc}%
    }

and

\newcommand\listoffigures{%
    \section*{\listfigurename}%
      \@mkboth{\MakeUppercase\listfigurename}%
              {\MakeUppercase\listfigurename}%
    \@starttoc{lof}%
    }

and in documentation we read

The code for \@mkboth is placed inside the heading to avoid any influence on vertical spacing after the heading (in some cases). For other commands, such as \listoffigures below this has been changed from the LATEX2.09 version as it will produce a serious bug if used in two-column mode (see, pr/3285). However \tableofcontents is always typeset in one-column mode in these classes, therefore the somewhat inconsistent setting has been retained for compatibility reasons.

Question Can any one please explain a bit this paragraph, in particular in some cases (so if there is an example)

and However \tableofcontents is always typeset in one-column

---

Update - Main questions

1. Why \@mkboth is placed inside the heading for \tableofcontents?
2. Why the two codes \tableofcontents and \listoffigures are differents?

Answers (what i understand)

\@mkboth is placed inside the heading to avoid any influence on vertical spacing after the heading (in some cases)

OK I can see the point here, but then the 2nd question come: why we don't do same for \listoffigures?

For other commands, such as \listoffigures below this has been changed from the LATEX2.09 version as it will produce a serious bug if used in two-column mode (see, pr/3285).

Here I can't see! and next lines confuse me more.