There are problems with procedural terrain, for one is the sheer size of the data if you populate the base data with alterations to the terrain base and expect to have buildings representative of specific regions, for the longest time OT didn't even have Biomes everything was green, there was 1 tree everywhere. Additionally the algorithms mean what you see at altitude is a procedural approximation of what you get as you get closer to the surface which is further procedurally defined. You might say "well if they overlay OSM data it'll be fine", not so, take a look at real roads, the earth around them is shaped almost always, we elevate them, slope them, cut into mountains. Defining a perfectly flat road segment takes x number of bytes in the octree, each segment has a defined start, end, texture, width, thickness, elevation and an enumeration for how it alters the terrain and probably many other things. Roads alone bloat the data set and we haven't even mentioned other natural and artificial features. The more you depart from the default dataset in the case of OT, the larger the storage requirement.
OT's representation of the earth is as a cube stored in an octree data structure (separated into a folder structure last I looked, +x, -x, +y, -y, +z, -z, each subdivided 4 times at the top level, as you get further down it's a lot like google maps, 1 big tile becomes 4 tiles per "zoom level", they then use an algorithm to "round out" the sides with an Earth Centred, Earth Fixed (ECEF) coordinate system. The base data they generate from is essentially NASA SRTM with 90m post spacing, it has to be translated into the OT native data structures for it to work much like roads and other features.
This is before we even consider the physics aspect required for high fidelity flight sim where the gravity vector points toward the origin instead of simply being a negative value on an (seem to remember y is vertical in DCS) axis. Other sims like FSX and X-Plane are more like DCS in that you're on a terrain treadmill. I used to work with VBS (as military) and even it had a curved earth rendering option from VBS 2 version 1.3 I think but that was back when we were only doing single large chunks of terrain up to 200km, maximum weapons employment range was generally 4km for any platform. Physics wise nothing changed, it employed flat earth physics as a pure shader implemntation.
I'm not saying ED can't achieve this in anyway, it's just a totally different beast that has been in development for years. With DCS you're talking changes to the underlying architecture, a significant workload and a large investment with less returns. You essentially have two choices, a handcrafted high detail area that has been checked extensively for quality (NTTR, vegas strip), or mass produced approximation and at times floating objects, mangled roads and so on.
