Yup, above are correct.
If you take a look at the final boss in Amdapor HM, you can get a max of 3 different text boxes that pop up and tell you that the magic to power the statue has faded from the stones embedded in it, among other things (I'll have to go back and either grab new screenshots, or see if I can find the ones I had prior).
Also, the text from the Kuribu card states it as well:
Created by the magi of Amdapor using an advanced form of golem construction, this statue is animated by the gems embedded in its chest and hands. Kuribu commands formidable white magicks to aid in its battle against invading voidsent.
It hasn't been outright stated how the Amdapor knew about what the Kuribu and winged lions looked like, more hinted at, especially when ShB was newer. The official answer was basically a "haha
idk, maybe you'll find out eventually" dodge to the answer, so either visions or visited by whatever could have done it... or they were old constructs from the Ancients, were found, and then they created the statues that way. I asked about it for the Fanfest lore/localization panel, so... perhaps we'll get an actual answer, maybe not.