Strange behaviour on the phrase_prefix query

Elastic Stack Elasticsearch
1

Hi,
I'm trying to run next query on the index:
"match": {
"folders": {
"query": "aqmkagm5mdizodk0ltg2ngbjltqxn2etotnmmc0wywy4m2vkmtg1mwealgaaaxfts4itp+bbtfaokkhwqimbaj1rfnbjd7voqhuq+f8apdiaaaibcqaaaa==",
"type": "phrase_prefix",
"operator": "OR",
"slop": 3,
"max_expansions": 20
}
}

and it's returns nothing, but when I run this query :
"match": {
"folders": {
"query": "aqmkagm5mdizodk0ltg2ngbjltqxn2etotnmmc0wywy4m2vkmtg1mwealgaaaxfts4itp+bbtfaokkhwqimbaj1rfnbjd7voqhuq+f8apdiaaaibcqaaaa=="
}
}

it's return results.
Am I missing something ? But, as far as I understand phrase_prefix should return in this case as well ?

Thanks