European Mac releases
The German localization of Oni for the Macintosh accidentally shipped with development-related files: level data for the Tool Mode editor and scripts for unreleased levels.
Discovery
Originally the community called this release "beta 5" because it was thought to come after the leaked beta 4; but in fact the extra files it contains would likely have come from Oni's pre-beta period. It was also called the "Big Blue Box beta" or the "BBB beta" because the discovery was made in a collection of four games called The Big Blue Box which included Oni. However, not only do all German copies of Oni for the Macintosh seem to have these files, but the French, Italian and Spanish localizations of Mac Oni have them as well. The U.S. release of Oni for the PS2 has the extra level scripts but not the tool files; the Japanese releases for Mac and Windows have the tool files but not the extra scripts.
Tool files
The tool files, used to present the in-game visual editor, are discussed HERE.
Extra level scripts
There are actually two peculiarities about the level scripts in German Mac Oni: first, they're the Windows level scripts (the Mac scripts have a few small differences). Second, there are scripts for additional levels not present in retail Oni: (a) test levels used by the developers, (b) a level which was later merged into other levels, and (c) an actual cut level. In total there are 10 folders not present in a retail Oni installation: Airport_II, BGI, aop, cap, CZ, CZ_II, global (empty), pit, ats, and SR. The missing levels which 9 of these folders refer to, and what the scripts reveal about them, are discussed at Pre-beta content#Cut levels.
Game app
The game app's creation date is Mar. 13, 2001, well after Oni's U.S. release; this is because the app was built anew from the source code after localization had occurred, and contains changes necessary to make it work with the extended set of characters in the German alphabet as well as to change the hardcoded strings "Save Point" and "Syndicate Warehouse" to their German translations. The game app itself has the same functionality, however, as other retail releases do; its version number is 1.1, just like the English Mac build of Oni, and access to Developer Mode and many BSL functions have been removed as in the English Mac builds of Oni.
Conclusions
In light of all the above, it seems that Oni's game data files were originally made available to the localization team during or before the beta period, but the source code for the game app was supplied after the Windows gold master, since separate files are present. The localizers did not understand which files were part of Oni's development and which were intended to be bundled with the game.