Checkbox comes with an install script to populate the ini files under /etc/checkbox.d from values which might be available in the debconf database. In order to determine which keys correspond to the checkbox package being intalled, the script looks at the templates file that used to be under the path /var/lib/dpkg/info/$pkg.templates. However, with recent multiarch support, the path is now /var/lib/dpkg/info/i386/$pkg.templates.
Since the checkbox packages are mostly arhitecture: all, it would be safe for most intents and purposes to interpolate the architecture of the host with dpkg --print-architecture. However, there have been discussions of reverting multiarch support which would require yet another update. Instead, it would be preferable to use dpkg-query --control-path $pkg templates which would work under all circumstances.