hi Rinndalir, maybe you never noticed, but slackpkg (not plus) does the same.
this is the bit (in /usr/libexec/slackpkg/functions.d/post-functions.sh) that finds *.new stuff
Code:
echo -e "\nSearching for NEW configuration files"
FILES=$(find /etc -name "*.new" ${ONLY_NEW_DOTNEW} \
-not -name "rc.inet1.conf.new" \
-not -name "group.new" \
-not -name "passwd.new" \
-not -name "shadow.new" \
-not -name "gshadow.new" 2>/dev/null)
as you can see it doesn't discriminate between files and directories.
to have it behave like you prefer, add a line
in that block, between the find arguments.