Are there any research-backed sources on cast iron seasoning?
it's applied chemistry so likely not going to find too many papers about it as not research per se.
but if you look at a site like serious eats you'll find a lot of discussion.
the reason to use a low heat oil like flax seed instead of olive oil is that the goal is to create a chemical change that will polymerise the oil to create a no stick surface to be able to sustain a very high heat itself when cooking.
YOu can get this with other oils to be sure - as has been the case for decades of folks using bacon drippings etc - but with its low smoke point it's pretty fast to do - and you can build up really thin layers quickly. The goal, again is to get that effect of a coating - it's not teflon but at least it's not plastic either.
if you look at the surface chemistry section in wikipedia on seasoning cookware you'll see more detail
https://en.wikipedia.org/wiki/Seasoning_%28cookware%29
and also this serious eats overview about cast iron is pretty good too
https://www.seriouseats.com/2014/11/the-truth-about-cast-iron.html
and
https://traditionalcookingschool.com/food-preparation/how-to-season-cast-iron/
and one more that claims to debunk flax seed oil as the best oil https://www.chowhound.com/post/testing-debunking-flaxseed-method-seasoning-cast-iron-807107