Arbitrary sections may not be supported by all man(1) implementations.
labwc manpages have numeric sections but installed in the wrong place:
$ meson setup --prefix=/usr _build && meson install -C _build
[...]
Installing docs/labwc.1 to /usr/share/man/man.1
Installing docs/labwc-config.5 to /usr/share/man/man-config.5
Installing docs/labwc-theme.5 to /usr/share/man/man-theme.5
Installing docs/labwc-actions.5 to /usr/share/man/man-actions.5
[...]