The restrictions changed last year, where the park decided to be more strict following long-term considerations after the Smiler incident.
Each ride has operating conditions set out by the manufacturer. In many cases, these aren't strict and have several variables related to them (a ride running for 10 hours straight is not going to stall the second the temperature goes 0.1C below the recommended temperature, for example). Merlin are now following these recommendations strictly though.
Following them strictly means that if the temperature does go below 0.1C or whatever, even for a second, the park stop running the ride, and require the temperature to be at the minimum operating temperature for a set period of time thereafter. It's a ridiculous system, as with something as complex as rides, a flat cut off condition - bar for extremes - is a bad idea.
So the conditions aren't new, but how the park view them is.