This is an improvement as it provides better data and has nothing to do with the models that are used in a separate step to forcast anything. But that is said in the article as well, with the satellite being the first hyperspectral view on Europe and North Africa.
I am not sure what to make if your question.
Ultimately better data will lead to and enable better models and forecasts, but I'm sure it's not super easy to put a number to that.
> I am not sure what to make if your question.
They are asking for a quantification of improvement. "better" predictions could range from "only experts notice" to "the daily/7 day weather is now noticeably more accurate for all citizens of Europe".