Cannot get -arg to work

[jemail99]

FreeBSD 14.0-RELEASE-p3
rocinante version: 0.1.20220714

template contains:

ARG FOLDER="nothing"
CMD echo ${FOLDER}

rocinante verify taisoft/folder produces:

Detected Bastillefile hook.
[Bastillefile]:
ARG FOLDER="nothing"
CMD echo ${FOLDER}

rocinante template taisoft/folder -arg FOLDER="storage" produces:

[TEMPLATE]:
Applying template: taisoft/folder...

[CMD]:
+ echo nothing
nothing
0

Template applied: taisoft/folder

I am not sure I'm understanding the -arg option and how to use it at all.
What am I doing wrong?

[apapsch]

Double -- it is: --arg