It makes sense from the lore in game and and the real world anthropological perspective. Auridon endgame is described as a buffer zone between mainland Tameriel and Somerset and that it is essentially a shield from pirates and invasions over the history of the first second third fourth eras. If you look at human history when you see one culture or group of people constantly subjected to warfare but the people next to them is not they tend to takeoff in two different culturally distinct directions.
This will show in armor clothing designs weapon ring architecture agricultural techniques and procedures as well as distinct cultures on morals ethics mores etc. but to just look at the buildings themselves from real world examples, in the United States the state of Florida all of their buildings and construction is set to a standard to withstand certain wind and storm levels due to constant threat of hurricanes many of the gulf coast states have similar requirements and they’re building codes. The state of California and much of the West Coast of the United States is subject to earthquakes so they’re building codes or set to Withstand earthquakes to a certain extent. The state of Texas last winter had a severe power outage due to a number of factors that I will not elaborate on completely due to ZOS’s user agreement on the forum but I will say the state of Texas being that it is a very warm and dry climate typically they do not have building codes set to withstand severe winter storms which is what happened last year and so their power grid completely buckled and there was a very bad tragic time frame for the people of Texas where they had no power/electricity. In the United States many homes have things like hardwood floors because wood and lumber is very common in the United States extremely abundant but if you go to places like Spain Italy Portugal Greece southern France most of southern Europe you will see lots of things like marble and travertine clay shingles and lots of concrete. Historically southern Europe has been rich in minerals and rock that has been useful in architecture but in in northern Europe rocks and minerals that are useful in architecture are very few you won’t find a lot of marble in England or the Scandinavian peninsula or Ireland. In short architectural design is a result of the resources found around the people living there that is available, socio/political and economic variables, developed building techniques, as well as personal artistic style and preferences of those people.
So it only makes sense that the high elves of auridon and their archetecture have a distinct style compared to mainland summerset.