First up, it doesn't make sense. Icathia is a Peninsula. It would've been tropical. Why would a sand troll live in the tropics? For the beaches? (However hilarious that would be I highly doubt it)
Consedering that
Icath’or is the name of the blood-bonded clan to which I was born, one with an honorable history of service to the Mage Kings.
and both Saijax and his childhood friend Colgrim were named Ichat'un, Ichat'un could be the name given to people who werent born in Icathia, but joined them after sometime. I mean, SaiJax literally means Desert Jax.
And second, we haven't known Jax's race for 13 years and if his race ever DOES get confirmed imagine how underwhelming a fucking sand-troll would be?
I genuinely would cry, it would be such a disgrace to Jax lovers.
thats just your opinion, we know almost nothing about Sad trolls, so call them underwhelming is a dangerous assumption.
Edit: I just noticed that Where Icathia Once Stood mentions this:
These men had grown up together, and had learned the secret ways of the warrior since they were old enough to hold a blade.
Shurimans didnt let Icathians use their weapons:
To bear Icathian armaments had been forbidden under Shuriman law...
Its unlikely that Saijax was a Shuriman, and most of the warriors from Icathia probally would be slave warriors so Saijax was trained since he was young in some warrior culture that much probally wasnt Icathia, this reinforces that he wasnt born in Icathia. A warrior culture training their children to be warriors fits a troll society.
is more likely to be a sand troll than 
funny that no one realised that. Look at how close the sand troll location is to Zaun.
