Well, the 2nd paragraph explains that: "The passwords are presumably for the “At the Pool” app rather than for the user’s Facebook account, but would put users at risk who have reused the same password across accounts."
Not to discount the possibility that the article could be incorrect about this, but it makes the claim quite unambiguously: "it contains plaintext (i.e. unprotected) Facebook passwords for 22,000 users"
> it contains plaintext (i.e. unprotected) passwords for 22,000 users
and
> The passwords are presumably for the “At the Pool” app rather than for the user’s Facebook account, but would put users at risk who have reused the same password across accounts.