I had to actually look up the raw, but like I thought it's even better. He didn't say "because of you", he said "because I like you". Specifically, "Nishikata ga suki dakara", which can mean either "because I like you (Nishikata)", or "because you like X" with some unknown, implied subject. Yeah, he follows up with "You like running, so I have to try hard or I'd never win", but even then it's pretty obvious, and I love that he did indeed straight-up declare his love. Again, since he also did so with the peppers.
Takagi was very direct a lot of the time, but Ooshiro seems much quicker to simply say how he feels, and I love it. Even if it's not terribly hard for her to find alternate interpretations.