Another thing about US soliders is they can become conditioned with their armor and weaponry in months. This compared to a ninja that has been training for years. Again. Conditioning. Conditioning, not random canon references, determines how a character uses their weapon.
Find me a conditioning exercise that allows one to carry a giant, dis-proportioned sword that physically could not even be swung, then we'll talk. Weight distribution alone changes the method behind this, if we want to start comparing the Narutoverse to real life. Actually, let's go just a little bit deeper. There's not a single real life reference anywhere regarding a man randomly carrying around a piece of metal weighing anywhere ranging between 25-75lb, and that's lowballing it. Who knows how heavy the Samehada was, who knows how heavy the Executioner's Blade was and thus far I don't see a specific weight on Shira's sword, so I just assume it's about 60% of the Executioner's Blade based on a single image reference.
My character doesn't need to be anything like Kisame or Suigetsu to know how to use their own weapon, whichwhich they grew up with nor should any of the other characters expected to either. Bringing up Kisame and other canon characters was absolutely pointless. No one was interested in why Suigetsu was exhausted using a large weapon. Did anyone say Suigetsu and Shira have the same constitution? Anyone mention they have the same level of training? Anyone bring up that they have been using large weapons the same period of time?
We're literally dwelling in a realm of complete impossibility. I present my logic with every case by comparing 'anchors' that we know of. Suigetsu, 16-17, apparent history and experience with swords, wields the most logical blade to use for comparison. The information I presented was not pointless. However, if you want, I will write you a novel every single time I post so that you can comprehend what I'm typing.