My measurements are done by putting my finger near the vents. And yes this easily produces more cold/cool air than the stock fan on the bullseye (my "before" setup).
Some of my motivation to do this was to reduce weight. I was thinking of doing x2 5015 mounted near the hot end in a pertsfang arrangement which to me looked heavy so gave the remote cooling a go. The tube do wobble a little but i think it is more the print head moving causing that rather than the air flowing in.
Defiantly not just for looks, I run the fans at 30% for normal printing and then pump it to an unnecessary 100% when printing bridges which come out perfect.
I guess the question you didn't ask: "is this over the top?" to which i say: yes, but why not :)
Also, since this i have replace the stock fan with a noctua 20x40mm which is overkill but was only $1 more than the 10x40mm and with this design i have the space.