Worth noting that you need iCloud active in the first place to opt-out of this feature, so it is still opt-in, since it is only ever defaulted to being on for users who proactively signed into iCloud.
Ah yes, you're right. I spoke to soon. I just checked on the latest Beta simulator and, sure enough, it is checked, with a fresh install and no iCloud account.
At least that proves the service is accessible anonymously (i.e., without an identifying iCloud token)
