When I had my "True Red Sea" regal from DD with the two smaller ones from Sumatra, I wasn't able to see the slightest difference in color.
From what I have seen so far, the Indian Ocean regals look all the same, regardless if they come from the Maldives or Sumatra. They have an orange-yellow chest, but the body background color is less pronounced orange-yellow. Also their black/blue & white stripes are wider.
Red Sea regals have a fairly uniform orange-yellow background color and their black/blue & white stripes are significantly narrower, giving them an overall more orange-yellow appearance.
I would say my "True Red Sea" regal and this last one listed by DD are Indian Ocean regals.
Who would that be?
As for Oman - it is too far away from the Red Sea for them to actually collect Red Sea fish there. All they can catch in their own waters are Indian Ocean and maybe some Persian Gulf fish. On top of that - to my knowledge - the Sultan of Oman doesn't allow fish collecting for the hobby in his waters. People tried to get a few Amphiprion omanensis as broodstock but only got refusals. The few omanensis that made it into the trade were either caught in adjacent waters (UAE or Yemen before the civil war) or on a scientific collection permit.
So whatever Oman exports on Red Sea fish must be collected somewhere else.