Ah yeah, that feels like old school track and field. I wouldn't take it that seriously. Like is it mature? No, but in my time in cross country and track when you weren't sweating your ass off doing long workouts and recovering from intense sprints, you'd just be screwing around with your teammates.
Honestly, I didn't see that much outside of what I've known with Inouei, she just seemed to talk down a bit to Kase, which is pretty normal since upper-classmen are not only responsible for training the younger runners but also set a strict example. It's just Yamada's fault and lack of knowledge specifically that causes her to overthink things, and see that weird bond between teammates in a sport that is all about competition and rigorous training as being girlfriends.
If anything, I'm more annoyed that Miwa was never able to read the room and kept pushing the senpai in front of Yamada's face.