End-to-end deep learning methods beat production weather forecast accuracy

This is strange to me because my understanding is that era5 is reanalysis data based on models and data assimilation (i.e. bayesian time series modeling). So they produced a machine learning model that predicted modeled data but not the raw data. But I could be completely wrong as Im not an expert on this.

link for era5 https://www.ecmwf.int/en/forecasts/datasets/reanalysis-datas...