Earlier quoted context omitted.
As far as I'm aware, iCloud for Messages is not enabled by default. Security-conscious users should know not to turn it on, though -- if iCloud servicing warrants is part of their threat model. Further, Apple ended up rolling out Advanced Data Protection for iCloud in 2023, so users who truly don't want Apple holding those keys can effectively take them from Apple. https://support.apple.com/guide/security/advanced-da…
Messages in iCloud is separate from the inclusion of the iMessage database in the regular iPhone iCloud backups. Could you check what that setting is set to on your newly setup device?
iCloud backup IS enabled. But Messages in iCloud is off.