ACME - Actions have no access to additionally generated certificate files.
The additionally generated certificate files are only available after the actions ("postscripts") have been run. This way, e.g., a shell command cannot access the generated files for further actions. I currently do not see an advantage/reason having the order like (a) execute actions -> (b) generate files.
I would create a pull request (if given an okay) moving the acme_write_all_certificates (https://github.com/pfsense/FreeBSD-ports/blob/v2.4.4_3/security/pfSense-pkg-acme/files/usr/local/pkg/acme/acme_command.sh#L80) before executing the actions.