Good point, I had forgotten about the master fisherman's story. But I just remembered something else - when you first arrive at FH, lots of people there talk about the Shumi and seem to know all about them; one guy asks what Squall thinks NORG is going to evolve into (of course Squall doesn't have a clue what he's talking about), the grease monkey aknowledges his close relationship with the artisan Shumi (which comes back in a side quest later), etc. Perhaps Esthar/FH had a closer relationship with the Shumi (or aliens) which led to there knowledge of technology.

Also, I think the Hyne/alien theory makes more sense; extra-terrestial beings of power appearing from the sky would seem god-like to those inhabiting the planet unaware that aliens exist. Even the sorceress power could be some manifestation of energy controlled by forces unknown to the inhabitants of the FF8 world. I mean if they can learn and control "para-magic," who is to say a more advanced species couldn't harness enough energy to possess a "sorceress power?"