This is often (though not always) blanket statement.
Logs are always generated, and logs include some amount of data about the user, if only environmental.
It's quite plausible that the spellchecker does not store your actual user data, but information about the request, or error logging includes more UGC than intended.
Note: I don't have any insider knowledge about their spellcheck API, but I've worked on similar systems which have similar language for little more than basic request logging.
Logs are always generated, and logs include some amount of data about the user, if only environmental.
It's quite plausible that the spellchecker does not store your actual user data, but information about the request, or error logging includes more UGC than intended.
Note: I don't have any insider knowledge about their spellcheck API, but I've worked on similar systems which have similar language for little more than basic request logging.