repro-33177.sh

#!/bin/bash

TMP_DIR=tmp_group_vars

mkdir -p $TMP_DIR/{dir,group_vars,inv}/

cat > $TMP_DIR/playbook.yml << EOF
- include: dir/playbook2.yml
EOF

cat > $TMP_DIR/group_vars/all << EOF
group_vars_variable_play: true
EOF

cat > $TMP_DIR/dir/playbook2.yml << EOF
- hosts: localhost
  tasks:
    - debug: var=group_vars_variable_play
EOF

touch $TMP_DIR/inventory
touch $TMP_DIR/inv/inventory

ansible-playbook -i $TMP_DIR/inv/inventory $TMP_DIR/playbook.yml

ansible-playbook -i $TMP_DIR/inventory $TMP_DIR/playbook.yml

rm -rf $TMP_DIR/