One much also take into account, this is the same dev team that gave Morning Lord "cleric" a + to INT.
This is due to Lore reasons.
Sun Elf is one of the Forgotten Realms Elf Subraces and it does get a +2 to Int (among other adjustments [-2 Con]).
Unfortunately the DDO devs played fast and loose with this one mostly due to the "Sun Elf" moniker, I must assume. Amaunator was/is a Netherese Deity and not a member of the Seldarine (FR Elven Pantheon).
Lore wise Sun Elves are amongst the most haughty and prideful of elven subraces and one would be safe to assume that they would worship
Elebrin Liothiel in matters pertaining to the Sun as he was the member of the Seldarine associated with the Sun Domain.
It is most certainly not a case of mistaken identity or cross-over worship either as Amaunator's look, personality, methods of worship, and even his domains greatly differ (aside from Sun) from those of Elebrin Liothiel.
Amaunator has had cross-overs with Lathander multiple times as they are both Human worshiped Sun Domain deities.