I briefly looked into this, and from what I remember these were all always based on the "satellite" based wind models which were interpolations of predictions at a very low resolution based on infrared. Winds aloft, as I'm sure you know, are often measured by radiosondes, but the subtle thing being that these samplings only make it into aeronautical forecasts, and at least in the US, stay US only, and don't bubble up to global summaries. These global data sets are not granular at all, and wouldn't provide the detail at different elevations. I wish such a data set was available... perhaps with the global satellite based ADS-B someone could do some kind of sampling based on live flight data, but I'm sure it would be a private (and costly) dataset.