Strange, but it seems that Xbox was releasing independent demos for both Xbox and Xbox 360 for some period in conjunction.
For example, the first demo promoting Xbox 360 was released in March 2006 http://redump.org/disc/60865/, however a demo promoting the original Xbox was also released in March 2006 http://redump.org/disc/20689/ and kept going utnil July 2006 (Demo #55 https://imgur.com/a/SbyJaFY https://trove.nla.gov.au/work/32949546? … 45027092).
To cloud the waters a bit more, there was some cross over content in which the early demos promoting Xbox 360 were formatted as OG Xbox (and therefore datted in redump as OG Xbox).
When I looked further into this, I noticed that the backs of the demos promoting Xbox 360 read "Xbox 360: The Official Australian Xbox Magazine" https://imgur.com/a/5qAAtku whereas the spines simply say "The Official Xbox Magazine", the same as OG Xbox (therefore a more confusing title).
I noticed this "Xbox 360" prefix in the UK demos as well: https://i.ebayimg.com/images/g/WwIAAOSw … -l1600.jpg
USA magazine demos don't seem to bare this same prefix https://www.ebay.com/itm/163557280482
However that's not surprising since the numbering continued from Xbox to Xbox 360 whereas the PAL regions reset the numbering back to Demo 01 when they started promoting X360.
As a result, I feel like it would be more accurate, less confusing to prefix the PAL X360 promoted demos as "Xbox 360: The Official Xbox Magazine Demo Disc". In addition, the Australian government catalogs the new series in the same way https://catalogue.nla.gov.au/Record/3623794
Usually I would just send this suggestion to Enker, but it might clear up some confusion for others.