This may be starting to sound like a broken record, but before WW I Guinness was a very different beer. At least the Extra Stout was. Foreign Extra Stout is still brewed to much the same gravity as 150 years ago. Few today realise that Extra Stout and Foreign Extra Stout used to be basically the same beer. The only difference was that the Foreign version was more heavily hopped and matured for longer, which meant that it was more attenuated and slightly stronger.
Two world wars have transformed the standard Stout into a totally different beer, while, in many respects, time has stood still for Foreign Extra Stout.
Modern style-obsessives classify standard Guinness as a "Dry Stout". But how long has Guinness fitted that profile? I suggest not very long. If you look at the table below, you'll see that there was a significant change in the degree of attenuation in 1950. Before that date it was in the range 72-75%. After 1950, it increased to between 81% and 86%. That must have had an impact on the character of the finished beer.
The normal story goes that English breweries made Sweet Stouts while Guinness and other Irish breweries brewed the stylistically different Dry Stout. Yet, if we look at English examples from the 1940's, some have a similar degree of attenuation to pre-1950 Guinness.
So is Dry Stout just another invented style? Probably.