Also very curious about what kind of model this is and how it could (so far as it sounds) take 100% of the hardware for 15 seconds per request.

My first instinct would be to do a one or two in the middle then both of the extremes. The assumption that it would be a normal distribution is so strange to me in this situation.

Yeah, this is like if you asked your friend how much more productive they think coffee makes them, and they replied with a four hundred thousand degree polynomial over the milliliter. Reality is never that predictable; reasonable people can recognize when they have run out of significant digits. Something has gone severely wrong in your data-modeling, your invocation of the model, or both. If it actually is doing compute for 15s, then to the extent that this works, it is wrapping a vastly simpler function, which I would suggest you graph and use going forward instead. It will save you the runtime, its outputs will be more reliable, and you will get actual insights.