Completion Suggester Sorting

Elastic Stack Elasticsearch
1

Hi,
I created an index that only contains the suggest property:

PUT /test
{
  "mappings": {
    "properties": {
      "suggest": {
        "type": "completion",
        "analyzer": "standard",
        "preserve_separators": false,
        "preserve_position_increments": false,
        "max_input_length": 30
      }
    }
  }
}

POST _bulk
{"index": {"_index": "test", "_id": "1"}}
{"suggest":{"input":["ab"]}}
{"index": {"_index": "test", "_id": "2"}}
{"suggest":{"input":["a bc"]}}
{"index": {"_index": "test", "_id": "3"}}
{"suggest":{"input":["a bc1"]}}
{"index": {"_index": "test", "_id": "4"}}
{"suggest":{"input":["a b"]}}

My doc data (also in the order returned by suggest => "ab"):

a b
a bc
a bc1
ab

GET /test/_search
{
	"suggest": {
		"suggest": {
			"completion": {
				"field": "suggest",
				"size": 100
			},
			"prefix": "ab"
		}
	}
}

When the weight is the same, the return result of completion is in lexicographical order. Why is the space not removed in this lexicographical order (considering "preserve_separators" : false )?
expected:

ab
a b
a bc
a bc123

or

a b
ab
a bc
a bc123

If it is possible, how should I configure the index?
Elasticsearch Version: 7.17.3
Thanks