wordpress_env_defaults:
  db_host: localhost
  db_name: "{{ site | underscore }}_{{ env }}"
  db_user: "{{ site | underscore }}"
  disable_wp_cron: true
  wp_env: "{{ env }}"
  wp_home: "{{ project.ssl.enabled | default(false) | ternary('https', 'http') }}://{{ project.site_hosts | map(attribute='canonical') | first }}"
  wp_siteurl: "{{ project.ssl.enabled | default(false) | ternary('https', 'http') }}://{{ project.site_hosts | map(attribute='canonical') | first }}/wp"
  domain_current_site: "{{ project.site_hosts | map(attribute='canonical') | first }}"
  git_sha: "{{ git_clone.after }}"
  release_version: "{{ deploy_helper.new_release }}"
  wp_debug_log: "{{ project_root }}/logs/debug.log"

site_env: "{{ wordpress_env_defaults | combine(vault_wordpress_env_defaults | default({}), project.env | default({}), vault_wordpress_sites[site].env) }}"

wordpress_env_defaults:
  db_host: localhost
  db_name: "{{ site | underscore }}_{{ env }}"
  db_user: "{{ site | underscore }}"
  disable_wp_cron: true
  wp_env: "{{ env }}"
  wp_home: "{{ project.ssl.enabled | default(false) | ternary('https', 'http') }}://{{ project.site_hosts | map(attribute='canonical') | first }}"
  wp_siteurl: "{{ project.ssl.enabled | default(false) | ternary('https', 'http') }}://{{ project.site_hosts | map(attribute='canonical') | first }}/wp"
  domain_current_site: "{{ project.site_hosts | map(attribute='canonical') | first }}"
  git_sha: "{{ git_clone.after }}"
  release_version: "{{ deploy_helper.new_release }}"
  wp_debug_log: "{{ project_root }}/logs/debug.log"
  wp_post_revisions: true

site_env: "{{ wordpress_env_defaults | combine(vault_wordpress_env_defaults | default({}), project.env | default({}), vault_wordpress_sites[site].env) }}"

Add ` wp_post_revisions: true` to `wordpress_env_defaults`
Add ` wp_post_revisions: true` to `wordpress_env_defaults` 

Complementing https://github.com/roots/bedrock/pull/572/