I'm curious if you lump me in with your belief of incorrect bow/arrow modeling based on your knowledge/beliefs... (not a dig at you - just genuinely curious)
I see no mention of Japanese Kyudo, Native American, American Survivalist, or the likes of Brazilian Amazon Kapoto which could round out your findings, and the vast differences in equipment; Including the natural use of two feather fletching (which somehow you find erroneous).
Also, four feather fletching is used as well, and three feather fletching is not the norm, but may be more popular, more used, or even more scientifically proven to maintain better/accurate flight. However, that does not negate the fact that if 3D modelers are creating them, that they should be considered cringe-worthy by their peers.
I do agree with your views that some create without any research, and the inaccuracies with the bow strings/bends. I found that to be the most difficult aspect of the bow build (self bow - Na'vi Native). To produce an accurate diameter bend to the bow with taut (sinew - or - hair) strings, while maintaining realistic movement/tension throughout the draw.
For the bow, I even went the extra mile and created string notches, but go unnoticed (unless one was to remove the string and sinew wraps).
The arrows are two feather fletchings bound by sinew and pitch. I could not find any source material that showed otherwise (for these particular arrows), and I believe the bow/arrow creation for the movies alien natives were based on research of our own planets native tribes hand-made works.
The arrows are also notched, and have attached glass or stone arrowheads with sinew and pitch.
Here are a couple of example renders by client:
Deep Forest Hunting
Tentska and Kawte :: Aerial Hunter
The Fight Continues
Only could find a couple of examples of bow draw (not clearest):
https://www.deviantart.com/drowelfmorwen/art/Tseo-teyr-Eywa-s-White-Child-57117636
Archer
And an example of utilizing another feather texture:
Wameyn :: Na'vi Commission
She does not make use of the plethora of arrow morphs I supplied, including shaft/feather/arrowhead deviations to make no one arrow the same, and wind on feather/feather flight morphs - including the feather fore-wisps.
If you would like to see modeling/test examples from me, please, let me know, and I will upload some...
One last thing of note: I read that many believed the 'new' grip/draw style employed by this movie was inaccurate, and impossible in real archery. Then I watched an expert archer on a weapons/archery show not only dispel the belief, but excel in the technique. He even admitted to liking the style...