From psql/help.c
    /*
    * Keep this line count in sync with the number of lines printed below!
    * Use "psql --help=variables | wc" to count correctly; but notice that
    * Windows builds currently print one more line than non-Windows builds.
    * Using the larger number is fine.
    */
    output = PageOutput(156, pager ? &(pset.popt.topt) : NULL);
uhm... this doesn't work at all with i10n, above all if respecting an
80 cols width.
Wouldn't be better to generate the output in a temp buffer after l10n,
count the line, then choose whether to use a pager or not?
Can provide a patch if you deem so.
-- Daniele