Finnish does have the new translations like for Before and After
strings.
I do have noted, though, that some improved translations have never made
it in. There's eg. one string in the partition wizard which is not in
line with the others (different translation for Guided), but the fixed
At least some of the translations you care about are, I believe, of
strings already translated in Debian. (Please read down to the end of
this comment, though.)
debian-installer's translations need to be updated by hand, since
they're used before language packs are installed. Updating them
