Package branch specification in openbsd_pkg module vs. package module

Greetings,

Attempting to understand why this difference exists installing a
package on OpenBSD 6.0 using the more general 'package' module vs. the
underlying installer module 'openbsd_pkg'. The package is given in
format supported for recent version of OpenBSD's package tools where
the branch can be specified using a '%' as the delimiter after package
name, hence below I use 'php%5.6' to install the PHP 5.6 branch from
package repo.

OS: OpenBSD 6.0 amd64
Python: 2.7.12 cpython
Ansible: 2.2.0.0

Value of variable used in tasks:

php_ver: "5.6"

Failure case task:

- name: install php
  package:
    name: "{{ item }}"
    state: present
  with_items:
    - "php%{{ php_ver }}"
  tags: [httpd, web_stack, php]

Result:

TASK [openbsd_httpd : install php]

Hi,

Any clarification possible on this question?

- Darren