I’m sure there is a maximum wind speed which would tie into the European Norm standard for theme park rides, which wasn’t around when The Big One was first opened. But wind speed is also quite complicated, because the effect of wind will depend on the direction. Also, wind tends to come in gusts, rather than blowing at a constant speed. In terms of the risk of a train valleying, it’s the wind combined with other factors such as temperature.
It is possible that the operating guidelines have changed. It’s possible that the way of measuring the wind speed has changed (for example if the anemometer is now in a different place). On modern rides you often have sensors and they’ll time how long it takes trains to get between them. If trains start taking too long the ride could also shut down, to prevent a train valleying. The ride has had its control system updated since the ride first opened, so it’s possible that time intervals have decreased or sensors have been moved.
To be honest, there are lots of things that could have changed, but whether they have done or not, I honestly don’t know.