We are not sure what or how "Earth" is defined. Thedas is not on the planet Earth, so we can assume Earth is well...earth, the stone, and in this case where the Titans dwell. Without knowing for sure, because of course...all of this is speculation, but it could be the Fade exists above the Stone, and the Veil created some "middle" like barrier.
Yea, what we don't know is the cosmology of Thedas.
But that is consistent with Skyhold being Solas' former place of operation. The hint being that we are holding up the sky, so to speak, by repairing the Veil.
It's not unusual for ancient societies to have seen the world as divided into threes. The heavens/sky (realm of the heavenly and sky dieites), the earth (realm of the earthly dieities, often referred to as titans or giants in mythology), and the underworld (underground, sometimes referred to as an abyss, chasm, or sometimes an ocean).
This looks to be somewhat similar to how they have modeled Thedas and it's lore.
Titans and Elvhen being at war would be normal, if their worlds were not the same. Dwarves do not have access to the fade, which backs up the theory that Fade is a realm of existence and does not exist everywhere at once or only exists in the minds of those connected to it.
A war between heavenly/sky gods and giants, and banished titans in the underworld... All common themes also.
The idea of all realms existing at the same time, like the fade being everywhere, is different. It suggests these realms are all just states of consciousness. That there is just one world, one reality, and one interconnected consciousness ultimately... starts to sound like Chantry ideas about the world, not ancient elven or dwarven. (That Solas echoes that idea is interesting)