Hey Kat Mechanics,
Thanks for the feedback!
Both the Sea Hunter Aatrox model and splash are wearing boots - the in-game model's appear to be open toed. While I agree that there should be consistency with the model and the splash, I think this is more of a minor detail, as compared to the color variation when the splash and model was released. Originally, the model was a completely different color from the splash, but, thanks to player feedback, the color was successfully changed to match the splash more.
Splash art for content is meant to give a general representation of what the content looks like. Of course, we can do a lot more with splash art than we can with in game models, which is why you'll often see some awesome detail in the splash art (take Arclight Vayne's cloth detail in her splash art, for example).
If you cruise through some splash art, you may notice bits here and there that aren't 100% accurate to in-game; it's usually about 95%. A lot of the time, things appear to be on the incorrect side of the champion, and that's due to the splash being flipped for composition, or so that it fits properly in the Champion Details page (the latter is more for when several champions are sharing the same splash art).
That said, the point you've brought up is certainly something we can pay more attention to in the future to better represent the in-game content via splash art.