Does running up some bleachers count as stretching or exercise?

I think it depends on duration. It's not a stretch, but could be considered exercise. Exercise is generally considered anything that raises your heart rate consistently for 10 minutes or more.

I don’t see a reason why the two need to be separate all the time! Something like Yoga is a great example of a way that you can combine both to create a peaceful more centered mind. I think it also depends on how fast you’re running and how far apart/how high the bleachers are. If you aren’t getting your knees up, there probably won’t be much stretch in your legs. Same goes for the arms, if you aren’t pumping them they aren’t getting any stretch. It’s definitely more on the cardio side in my mind, but I don’t think you can completely count out stretching as well.

I think it’s more of exercise. Stretching is something static to me, holding not fully comfortable but yet not painful pose.