As I understand it, the concern is that a glancing impact is likely to impart rotational accelerations to the head as the helmet "sticks" to a rough surface like asphalt.. Given the complex nature of just about any head impact, I'd assume few are a "straight smack". So your question is probably more like, "How often is the MiPS system going to be presented with harmful amounts of possible rotational acceleration (glancing strikes) that MiPS needs to render harmless?" I don't know the answer, but here's the paper describing the Virgina Tech testing methods and there is some discussion about rotation in it. https://vtechworks.lib.vt.edu/items/...7-a4eef66ad1fa

There are references in this article that may help answer the question. https://www.nature.com/articles/s41598-022-11559-0
But frankly, I don't see how MiPS is likely to be harmful. I can get it in a highly rated and inexpensive helmet. So I'm not highly motivated to dig further. If you do dig in, I'd be curious to know what you found though.