Assigned variable doesn't match when it's on the left side of a constraint

[
    {
        "RuleSet": {
            "name": "demo",
            "hosts": [
                "localhost"
            ],
            "sources": [
                {
                    "EventSource": {
                        "name": "ansible.eda.generic",
                        "source_name": "ansible.eda.generic",
                        "source_args": {
                            "payload": [
                                {
                                    "xyz": 300,
                                    "pr": 456
                                },
                                {
                                    "prs_list": [
                                        456,
                                        457
                                    ]
                                }
                            ]
                        },
                        "source_filters": []
                    }
                }
            ],
            "rules": [
                {
                    "Rule": {
                        "name": "r41",
                        "condition": {
                            "AllCondition": [
                                {
                                    "AssignmentExpression": {
                                        "lhs": {
                                            "Events": "varname"
                                        },
                                        "rhs": {
                                            "EqualsExpression": {
                                                "lhs": {
                                                    "Event": "xyz"
                                                },
                                                "rhs": {
                                                    "Integer": 300
                                                }
                                            }
                                        }
                                    }
                                },
                                {
                                    "ItemInListExpression": {
                                        "lhs": {
                                            "Events": "varname.pr"
                                        },
                                        "rhs": {
                                            "Event": "prs_list"
                                        }
                                    }
                                }
                            ]
                        },
                        "actions": [
                            {
                                "Action": {
                                    "action": "debug",
                                    "action_args": {
                                        "msg": "Assignment works"
                                    }
                                }
                            }
                        ],
                        "enabled": true
                    }
                }
            ]
        }
    }
]