Nice one there, much simpler than my nearly POSIX one (I think I rely on a GNU sed extension, but it was years since I wrote this):

  shuf /nix/store/ny99jkpl3r9zgkkdv5apprzl18i8rb4m-scowl-2019.10.06/share/dict/wbritish.txt \
    | grep '^[A-Za-z]\+$' \
    | head -n 3 \
    | sed -e 's|\(.\)\(.*\)|\u\1\2|g' \
    | tr -d '\n' \
    | sed -e 's|$|\n|g'

Which gives you for example:

  OmegasInsentientPantheons

I only use this for “secret” questions though, not passwords.