Why does the BM25 keyword search return docs that don't contain query terms?

[lingvisa]

from langchain_community.retrievers import BM25Retriever
from langchain_core.documents import Document

retriever = BM25Retriever.from_documents(
    [
        Document(page_content="foo"),
        Document(page_content="bar"),
        Document(page_content="world"),
        Document(page_content="hello"),
        Document(page_content="foo bar"),
    ]
)

results = retriever.invoke("windy london")

for result in results:
    print(result)

The query 'windy london' will return:

0 page_content='foo bar'
1 page_content='hello'
2 page_content='world'
3 page_content='bar'

All the returned docs don't contain the query terms 'wendy london'. Why is that? I tested the same query in the original code, rank_bm25, it doesn't return docs that don't contain query terms, as blow:
https://github.com/dorianbrown/rank_bm25