I don't understand what you find odd about "affecting IOPS."

If someone does something that has an impact on IOPS, then it's sensible to say they (or what they're doing) are "affecting IOPS."

Screaming at the JBOD wasn't "causing" IOPS, so using that phrase would've been more confusing.

Right, I covered that in my edit which I probably made as you were writing your post. It was just one of those situations where a small amount of confusion compounds until you have lost sight of reality.