First, here's the German data:
And here's the Italian series:
This is why I see the vernacular prognostications rather than Latin practicas as the driving force behind the development of the genre in Germany. The Latin production barely increases after 1490 (and declines precipitously in the sixteenth century). Already in 1486-1490, the majority of expansion in production is coming from vernacular editions. Italian vernacular expansion comes later, and doesn't displace Latin. In addition to the differences in format, organizational structure, and content, the different language preferences are one more reason why I think that practicas had different functions north and south of the Alps.