---
- name: Set stats test - node1
  hosts: all
  become: true
  gather_facts: false

  vars:
    bigboot_size_target: 1G

  tasks:
    - name: Test a var
      ansible.builtin.set_stats:
        data:
          __bigboot_size_target: "{{ bigboot_size_target }}"
          __bigboot_adjacent_lvm: "/dev/mapper/system-root"
          __bigboot_execute_bigboot: true
          __bigboot_execute_shrink: "true"
          bigboot_size_target: "{{ bigboot_size_target }}"
          bigboot_skip_rear_backup: "{{ bigboot_skip_rear | default('false') }}"
        per_host: false
        aggregate: false

    - name: Debug test_set_stats
      ansible.builtin.debug:
        msg: "Locally we use bigboot_size_target -> {{ bigboot_size_target }}"

...