So on that basis two passengers who fly Europe-dxb one who ends in Dubai and one who flies onward from Dubai to say Australia and who are both downgraded on Europe-dxb only would receive different compensation. So if that is the case airlines should insist on a new ticket from dxb onwards to avoid this.

Seems the punitive is the 75% refund on that leg. That is likely more than the fare difference so would count .

Seems like the ambiguous wording will be amended to reflect the relevant leg of the journey and in the meantime we have some test cases courtesy of this forum to see how current wording is viewed.