I dont think arctic f12 case fan is optimized for pressure... I was planning to buy arctic p12(optimized for static pressure) 120mm fan... I saw the reviews, and it was amazing. (close to noctua).
That may be right that it's not optimised for pressure but the results speak for themselves.
I think we're too prone (all of us) to fall into a logic hole but the reality is that sometimes a random fan might just do the job as well as an 'optimised' fan.
I'm going to be actively doing this now with other used GPUs I get my hands on from an experimentation point of view and it's something I've also done in the past as well. I think I actually sold a GPU on ebay like that with a fan strapped on to it with zip ties.
A fan is a fan at the end of the day and the tiny fans on the GPU coolers are not really what'd you'd call optimised for pressure but a 120mm fan is always bigger than any of the GPU cooler fans that are 80mm-90mm.
I don't know why they don't release any GPU coolers with 120mm fans on them.. perhaps they don't want clearance issues with some cases.. who knows.. in any case I've got 2 of these GPUs in my son's and wife's desktops and the cooling performance is better than before. It doesn't look pretty, in fact on one of them I was so lazy I just strapped it on with 2 rubber bands (I'll zip tie them eventually).
Food for thought.