Generally, when most programmers are experimenting with failed builds they either state that that version had "no changes" or they skip over that version number (leaving it as an internal build) and move on to the next build.
There is no hard and fast rule, or even a real need to do this but a change in version number in and itself implies that changes have been made; even if that isn't necessarily part of the process of making a new build. Stating that the changes to a ROM are "Private" does not indicate that no changes have not been made, it implies exactly the opposite: that changes have been made.
By marking these changes as "Private" you imply that you have something to hide, even if you may not. When working with something that has such sensitive access to users' personal data, this attitude does not usually engender trust among your users.