It is not strictly true.
IPA's came about as they needed to be strong in alcohol to survive the journey to India back when we colonised it, hops also have anti-bacterial qualities so this added to the preservation of the beer.
You can make a low abv beer hoppy, as you point out that Brewdog have. It all depends on when you put the hops in the boil, early they give you bitterness, late in the boil/dry hopping you get more of the aromas.
Higher strength beers such as DIPA are just the current trend, I've found most are very imbalanced and too sugary/malty for my tastes.
In other words, it's bollocks