That is pretty much what I read/heard. It really effects the trajectory at longer ranges. From what I understood the norm is skinny arrows and low profile fletches for much less drag.
The explanation I got was that you didn't need the extra stabilization because the arrow has much more time and distance to stabilize on it's own. Versus shooting at closer distances and having to force the arrow to stabilize much quicker. Also it was mentioned that more FOC and especially more drag could effect the arrows consistancy from arrow to arrow at much longer ranges. Like if one arrow had slightly more drag than another it could effect it's impact point farther down range. Something you wouldn't notice at 20 or 30 yards, but would have a large impact at 70-90 meters. So the less drag and more arrow dynamic the arrow the better it would slip thru the air and be more consistant from arrow to arrow.
Again, only going by what I have read on the net and what one guy told me a few years ago at a club. I have no real first hand experiance on the subject as you do. I used to practice at 70 meters sometimes, but honestly wasn't what I would good at that distance. Every now and then I could pull myself together and get 3 arrows to group in a few inches, but mostly fist sized or bigger groups.
I like to do it because at that distance you can really tell if you are doing something wrong with your form or grip. If you pull a shot you really PULL a shot
.
I tend to agree with your thoery of thinking though. If you are shooting at known distances who give a rats butt how fast the arrow is going. When I shot spots I would see guys shooting light arrows with straight vanes and hunting type draw weights. The heck with that, I shot arrows with LOT's of fletch and lower draw weights. Why wear myself out, and who cares how fast the arrow gets there? I did a lot of playing though, as far as trying different arrows, releases, rests and the such. It wasn't uncommon for my set up to be different every week. Doesn't do much for your scores, but I had fun. I really just wanted a warm place to shoot in the winter. I wasn't there to win anything.
Paul