I was doing more experiments, and it looks like a Ch 1 OTA channel in the 722 guide, maybe actually pointing to a Ch 1 VOD on both my 722s.
The first picture shows that 1 - VOD is locked, but not the 001-xx OTA channels.
The second picture shows that locked channels are hidden, and that the system is locked.
The third picture shows that when I try to tune to OTA channel 001-01, as confirmed by the dark green to the right of the attention popup, I am prompted for a password. There are no rating locks set, and channel 001-01 (What) was not locked. So, I should not be prompted for a password here. I believe that the only reason the receiver would be prompting for a password, would be if it thinks I am ordering a PPV/VOD, instead of tuning in to the OTA channel. Note that I have not tried entering the password, as I do not want to accidently order something.
Now OTA channel 001-02 (Family) does not prompt me for a password. So, I tuned to it. However, pressing either "browse" (Picture 4) or "guide" (Figure 5) makes it look like I might be on a VOD channel. i.e. The bottom banner belongs to "The Descendants" in browse, and/or the guide goes directly to the 1 VOD "The Descendants" channel instead of channel 001-02 "Family". Note that no arrow keys were pressed.
This is easily reproducible multiple times on both my 722s. So, I suspect that it maybe possible to accidently order a PPV, especially if PPV is not locked.