Ultima Weapon?

[Singularity]

Is it documented anywhere that the Heart of Sabik was installed by the Garleans? It doesn't seem to make sense to me.

When Lahabrea is talking about it just before he activates it to cast Ultima, he mentions that it's something "whose surface even the vaunted scholars of ancient Allag failed to scratch", meaning the Allagans certainly had access to it, yet apparently they did nothing at all with it?. From a visual standpoint, the Heart seems pretty well-integrated into Ultima's upper torso. It looks, to me at least, like it was designed to be there from the start.
He also states that it is "the weapon's core" and he does so in a way that suggests he is telling Gaius this for the first time. Might just be my own skepticism, but I find it somewhat unlikely both that the Garleans had the technical ability to replace the very core of an Allagan weapon (though I admit it may have been done under Ascian instruction) and that Gaius was not kept informed of this at all considering it was his flagship project.

As an aside, if the Heart was added by the Garleans, then it seems likely that "The Ultima Weapon" is not the thing's original name, as the Allagans would never have heard of Ultima. Barring a remarkable coincidence, it would probably have been named that by Lahabrea when explaining to Gaius what the thing was.