Do you have evidence that this is a fact? Have you looked at the computing requirements documents for, for example, stock exchanges?
I have it on good evidence that stock exchanges ran on mainframes. They are essentially the counterparty (in a computing sense not a financial sense) in each placed order.
If someone is willing to run a fiberoptic cable from Chicago to New York or New Jersey to exploit reduced propagation delay, admittedly much larger than a refresh stall, wouldn't you think that they or someone else would also be interested in predicting computing stalls. An exchange would face at least a significant reputational risk if it could be exploited that way.
The low latency matching engines in colos run Linux these days, and we use microwave instead of fiber. Incoming orders are processed by hardware receive timestamp, so predicting jitter doesn’t give you an advantage. Clearing and settlement I’m not sure about, not latency critical though, mainframes wouldn’t surprise me there.
