I suspect there has been a glitch in the allocation of the sub regions, which Ancestry are trying to fix in the background.
My own sub regions initially came out as the North Highlands, Northern Islands and the Isle of Man (I think). The Isle of Man and Northern Islands had gone by the next morning. Today, I notice that I am back to a subregion of Scottish Highlands and Central Lowlands, which given that my family are pretty much universally from Ayrshire, Argyll, West Lothian, Stirlingshire and Lanarkshire seems a reasonable fit.
I will freely admit to being one of those who regarded "ethnicity" as little more than an amusing conversation piece, and I would still argue that DNA companies offering to find "Neanderthal" or "Viking" DNA are bordering on fraudulent, but upon reading the explanations provided by Ancestry I am confident that whilst far from perfect, the results do predict pretty accurately what the science part says they do.
In fairness, it must be said, Ancestry are hardly guiltless here, since the problem is most people think the ethnicities (or Ancestral Regions as they are now) represent something entirely different than they actually do because of the marketing campaigns. Ultimately, Ancestry, just like it's competitors, is a business, so of course they do things in part to sell kits and or subscriptions, but sometimes that gets in the way of what many of us think should be their primary concern which is the genealogy. I for one could do without the traits in their entirety, but I recognise why Ancestry are devoting time and effort to adding them.
Returning to the Ancestral Regions, what I would say is this. In researching our trees, we all know the perils of copying other people's research and accepting it as accurate without going to the source material. We all share a rather scathing view of those who seem more interested in "filling" their tree than checking for accuracy. I suggest that in understanding the validity of DNA results the same approach applies. Go to the source or simply copy each other's scepticism.
Ancestry provides lengthy and detailed descriptions of how they assemble their results and what they actually mean. If after reading the source material you still think it is all just smoke and mirrors, fine. After all, we all know some statutory registers are a little economical with the truth, so not all source material is accurate.
Or don't bother. Just the next time you sneer at someone's unsourced tree, take a moment to think - am I really any different?