This menu contains information about the system build, repository, revision,… doesn’t look like it’s super useful information for now, but still interesting I guess.
The combination to get this menu to show requires practice but I could confirm it works on my vita (Firmware 1.510).
Go to Settings > System > System Information
Press simultaneously RTrigger + LTrigger + DPad Left + Square for a few seconds
Release those buttons then immediately press the start button
tadaa, additional information shows up